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PHILOSOPHICAL 


TRANSACTIONS 

OF THE 

ROYAL SOCIETY 

OF 

LONDON. 


FOR THE YEAR MDCCXCIII. 


PART I. 


LONDON, 


SOLD BY PETER ELMSLY , 
PRINTER TO THE ROYAL SOCIETY. 
MDCCXCIII. 



J 


ADVERTISEMENT. 


The Committee appointed by the Royal Society to direct the pub- 
lication of the Philosophical Transactions, take this opportunity to ac- 
quaint the Public, that it fully appears, as well from the council- 
books and journals of the Society, as from repeated declarations which 
have been made in several former Transactions, that tire printing of 
them was always, from time to time, the single act of the respective 
Secretaries, till the Forty-seventh Volume: the Society, as a Body, 
never interesting themselves any further in their publication, than by 
occasionally recommending the revival of them to some of their Secre- 
taries, when, from the particular circumstances of their affairs, the 
Transactions had happened for any length of time to be intermitted. 
And this seems principally to have been done with a view to satisfy 
the Public, that their usual meetings were then continued, for the im- 
provement of knowledge, and benefit of mankind, the great ends of 
their first institution by the Royal Charters, and which they have ever 
since steadily pursued. 

But the Society being of late years greatly enlarged, and their com- 
munications more numerous, it was thought advisable, that a Com- 
mittee of their members should be appointed to reconsider the papers 
read before them, and select out of them such as they should judge 
most proper for publication in the future Transactions ; wl i;h was 
accordingly done upon the 26th of March, 1752. And tl c grounds 

A 2 


of their choice are, and will continue to be, the importance and sin- 
gularity of the subjects, or the advantageous manner of treating them; 
without pretending to answer for the certainty of the facts, or pro- 
priety of the reasonings, contained in the several papers so published, 
which must still rest on the credit or judgment of their respective au- 
thors. 

It is likewise necessary on this occasion to remark, that it is an esta- 
blished rule of the Society, to which they will always adhere, never to 
give their opinion, as a Body, upon any subject, either of Nature or 
Art, that comes before them. And therefore the thanks, which are 
frequently proposed from the Chair to be given to the authors of such 
papers as are read at their accustomed meetings, or to the persons through 
whose hands they receive them, are to be considered in no other light 
than as a matter of civility, in return for the respect shewn to the So- 
ciety by those communications. The like also is to be said with re- 
gard to the several projects, inventions, and curiosities of various 
kinds, which are often exhibited to the Society; the authors whereof, 
or those who exhibit them, frequently take the liberty to report, and 
even to certify in the public news-papers, that they have met with the 
highest applause and approbation. And therefore it is hoped, that no 
regard will hereafter be paid to such reports, and public notices; which 
in some instances have been too lightly credited, to the dishonour of 
the Society. 


CONTENTS. 


I. An Account of two Rainbows , seen at the same Time , at 
Alverstoke, Hants, July 9, 1792. By the Rev. Dr. Sturges. 
Communicated by William Heberden, M. D. F. R. S. page 1 

II. Description of the double horned Rhinoceros of Sumatra.. By 

Mr. William Bell, Surgeon in the Service of the East India 
Company, at Bencoolen. Communicated by Sir Joseph Banks, 
Bart. P.R.S. p. 3 

III. Description of a Species of Chcetodon, called, by the Malays, 

Ecan bonna. By Mr. William Bell, Surgeon in the Service of 
the East India Company, at Bencoolen. Communicated by Sir 
Joseph Banks, Bart. P. R. S. p. 7 

IV. Account of some Discoveries made by Mr. Galvani, of 

Bologna ; with Experiments and Observations on them. I?i 
two Letters from Mr. Alexander Volta, F. R. S. Professor of 
Natural Philosophy in the University of Pavia, to Mr. Ti- 
berius Cavallo, F. R. S. p. 10 

V. Further Particulars respecting the Observatory at Benares, 

of which an Account, with Plates, is given by Sir Robert 
Barker, in the LXVIIth Vol. of the Philosophical Transactions. 
In a Letter to William Marsden, Esq. F. R. S, from John 
Lloyd Williams, Esq. of Benares. p. 45 


C vi 3 

VI. Extracts of two Letters from the Rev. Edward Gregory, 

M. A. Rector of Langar, Nottinghamshire, to the Rev .. 
Nevil Maskelyne, D. D. F. R. S. Astronomer Royal ; con- 
taining an Account of the Discovery of a Comet , with Obser- 
vations thereon. p. 50 

VII. Observations of the Comet of 1793, made by the Rev „ 
Nevil Maskelyne, D. D. F. R. S. Astronomer Royal, and 
other Observers. Communicated by the Astronomer Royal, p. 55. 

VIII. Account of the Method of making Ice at Benares. In a 

Letter to William Marsden, Esq. F. R. S. from John Lloyd 
Williams, Esq. of Benares. p. 56. 

IX. Account of two Instances of uncommon Formation, in the 

Viscera of the Human Body. By Mr. John Abernethy, As- 
sistant Surgeon to St. Bartholomew's Hospital. Communi- 
cated by Sir Joseph Banks, Bart. P. R. S. p. 59 

X. An Account of the Equatorial Instrument. By Sir George 

Shuckburgh, Bart. F. R. S. 67 

XI. Additional Observations on the Method of makbig Ice at 

Benares. In a Letter to William Marsden, Esq. F. R. S. 
from John Lloyd Williams, Esq. of Benares. p. 129 

APPENDIX. 

Meteorological Journal kept at the Apartments of the Royal So - 
cieiy, by Order cf the President and Council . 













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- 





















. 








s 




























' 




















THE President and Council of the Royal Society adjudged, 
for the year 1792, the Medal on Sir Godfrey Copley’s Donation, 
to Sir Benjamin Thompson, now Count of Rumford, for his various 
Papers on the Properties and Communication of Heat. 


PHILOSOPHICAL 


TRANSACTIONS. 


I. An Account of two Rainbows , seen at the same Time , at 
Alverstoke, Hants, July 9, 1792. By the Rev. Mr. Sturges, 
Communicated by William Heberden, M.D. F. R. S. 


Read January 10, 1793. 

On the evening of the 9th of July, 1792, between seven and 
eight o'clock, at Alverstoke, near Gosport, on the sea coast of 
Hampshire, there came up, in the south-east* a cloud with a 
thunder-shower; while the sun shone bright, low in the hori- 
zon to the north-west. 

In this shower two primary rainbows appeared, AB and 
AC, (Tab. I.) not concentric, but touching each other at A, in 
the south part of the horizon ; with a secondary bow to each, 
DE and DF (the last very faint, but discernible), which 
touched likewise, at D. Both the primary were very 
vivid for a considerable time, and at different times nearly 
equally so ; but the bow A B was most permanent, was a 
larger segment of a circle, and at last, after the other had 
vanished, became almost a semicircle ; the sun being near 
^-mdccxciii. B- 


z Dr. Sturges's Account of two Rainbows. 

setting. It was a perfect calm, and the sea was as smooth 
as glass. 

If I might venture to offer a solution of this appearance, it 
would be as follows. I consider the bow A B as the true one, 
produced by the sun itself; and the other, AC, as produced 
by the reflection of the sun from the sea, which, in its per- 
fectly smooth state, acted as a speculum. The direction of 
the sea, between the Isle of Wight and the land, was to the 
north-west, in a line with the sun, as it was then situated. 
The image reflected from the water, having its rays issuing 
from a point lower than the real sun, and in a line coming 
from beneath the horizon, would consequently form a bow 
higher than the true one, AB. And the shores, by which 
that narrow part of the sea is bounded, would, before the sun's 
actual setting, intercept its rays from the surface of the water, 
and cause the bow AC, which I suppose to be produced by 
the reflection, to disappear before the other. 


Fhdos Trans MDCCXCHI. TaJ>. I 


F *■ 



.Jfiaj'ih- o. Jr. 




C 3 3 


II. Description of the double horned Rhinoceros of Sumatra. By 

Mr. William Bell, Surgeon in the Service of the East India 

Company, at Bencoolen. Communicated by Sir Joseph Banks. 

Bart. P. R. S. 

Read January 10, 1793. 

The animal herein described was shot, with a leaden ball 
from a musket, about ten miles from Fort Marlborough. I 
saw it the day after ; it was then not in the least putrid, and 
I put it into the position from which the accompanying 
drawing was made. (See Tab. II.) 

It was a male, the height at the shoulder was four feet four 
inches ; at the sacrum nearly the same ; from the tip of the 
nose to the end of the tail, eight feet five inches. From the 
appearance of its teeth and bones it was but young, and pro- 
bably not near its full size. 

The shape of the animal was much like that of the 
hog. The general colour was a brownish ash ; under the 
belly, between the legs and folds of the skin, a dirty flesh 
colour. 

The head much resembled that of the single horned rhino- 
ceros. The eyes were small, of a brown colour; the mem- 
brana nictitans thick and strong. The skin surrounding the 
eyes was wrinkled. The nostrils were wide. The upper lip 
was pointed, and hanging over the under. 

There were six molares, or grinders, on each side of 

B 2 


4 


Mr. Bell’s Description of the 

the upper and lower jaw, becoming gradually larger back- 
ward, particularly in the upper. Two teeth in the front of 
each jaw. 

The tongue was quite smooth. 

The ears were small and pointed, lined and edged with 
short black hair, and situated like those of the single horned 
rhinoceros. 

The horns were black, the larger was placed immediately 
above the nose, pointing upwards, and was bent a little back ; 
it was about nine inches long. The small horn was four inches 
long, of a pyramidal shape, flattened a little, and placed above 
the eyes, rather a little more forward, standing in a line with 
the larger horn, immediately above it. They were both 
firmly attached to the skull, nor was there any appearance of 
joint, or muscles to move them. 

The neck was thick and short, the skin on the under side 
thrown into folds, and these folds again wrinkled. 

The body was bulky and round, and from the shoulder ran 
a line, or fold, as in the single horned rhinoceros, though it 
was but faintly marked. There were several other folds and 
wrinkles on the body and legs ; and the whole gave rather the 
appearance of softness. 

The legs were thick, short, and remarkably strong ; the 
feet armed with three distinct hoofs, of a blackish colour, 
which surrounded half the foot, one in front, the others on 
each side. The soles of the feet were convex, of a light co- 
lour, and the cuticle on them not thicker than that on the foot 
of a man who is used to walking. 

The testicles hardly appeared externally. 

The penis was bent backward, and opened about eighteen 


double horned Rhinoceros of Sumatra. 5 

inches below the anus. At its origin it was as thick as a 
man's leg, and about two feet and a half long ; the bend in it 
occasions the urine to be discharged backwards. The glans is 
very singular : the opening of the urethra is like the mouth 
of a cup with its brim bending over a little, and is about three 
quarters of an inch in diameter ; the glans here is about half 
an inch in diameter, and continues that thickness for an inch 
and a half ; it is then inserted into another cup like the first, 
but three times as large. The glans afterwards gradually be- 
comes thicker, and at about nine inches from the opening of 
the urethra are placed two bodies on the upper part of the 
glans, very like the nipples of a milch cow, and as large ; 
these become turgid when the penis is erected. The whole 
of this is contained in the prepuce, and may be considered as 
glans. 

From the os pubis arises a strong muscle, which soon be- 
comes tendinous. This tendon is continued along the back, or 
upper part, of the penis ; it is flattened, is about the size of a 
man's little finger, and is inserted into the upper part of the 
glans, near the end. The use of this muscle is to straiten 
the penis. 

On the under side of the penis there are two muscles, anta- 
gonists to the above ; they arise from the os ischium fleshy, 
run along the lower side of the penis, on each side of the cor- 
pus spongiosum, and are inserted fleshy into the lower side of 
the glans. The action of these muscles will draw in the penis, 
and bend it. 

The male has two nipples, like the female, situated between 
the hind legs, they are about half an inch in length, of a py- 
ramidal form, rounded at the end. 


6 Mr. Bell's Description of the double horned Rhinoceros , &c. 

The whole skin of the animal is rough, and covered very 
thinly with short black hair. The skin was not more than 
one third of an inch in thickness, at the strongest part ; under 
the belly it was hardly a quarter of an inch ; any part of it 
might be cut through with ease, by a common dissecting knife. 

The animal had not that appearance of armour which is ob- 
served in the single horned rhinoceros. 

Since I dissected the male, I have had an opportunity of 
examining a female, which was more of a lead colour ; it was 
younger than the male, and had not so many folds or wrinkles 
in its skin, of course it had still less the appearance of armour. 

The only external mark which distinguishes it from the" 
male is the vagina, which is close to the anus ; whereas, in 
the male, the opening for the penis is eighteen inches below 
the anus. 

Tab. II. Represents the entire animal. 

Tab. III. The cranium. 

Tab. IV. The upper and under jaw, separated from each 
other. 








Fhdos. Trans. MDCCXCEL^. lll./r 6. 










Philos. Trans. MDCCXC1II. Tab. W. p. 6. 


So ajit'c . Sc. 










C 7 3 


III. Description of a Species of Chatodon , called, by the Malays, 
Ecan bonna. By Mr. William Bell, Surgeon in the Service of 
the East India Company, at Bencoolen. Communicated by Sir 
Joseph Banks, Bart. P. R. S. 

Read January 17, 1793. 

The fish called Ecan bonna, by the Malays, is broad, flat, 
and of a lead colour ; the belly is flat, white, and in places 
tinged with green. The eyes are a bright yellow. The body 
is covered with small semicircular scales. 

Its length is generally about eighteen inches ; its breadth 
thirteen, and, at the thickest part, it is nearly three inches 
thick. 

It is frequently caught at Bencoolen, and several other 
parts on the west coasts of Sumatra, and is said to grow to a 
much larger size. Its flesh is white, firm, and well flavoured, 
and it is considered as a good fish for the table. 

It has six fins : two pectoral, two ventral, one dorsal, and 
one anal fin. The tail is broad, and of a triangular form. 

The pectoral fins are small, blunted at their ends, and 
placed a little behind the gills. 

The ventral fins are placed on the sternum, and are longer, 
and more pointed. 

The dorsal fin arises at the beginning of the spinous pro- 
cesses of the back, and is continued down nearly to the tail. 
The anal fin arises a little below the anus, and is also conti- 


8 


Mr. Bell's Description of 

nued on almost to the tail. It is strong and broad, like the 
dorsal, and projects a little farther backward than it. 

The mouth is small, and each jaw contains five rows of 
small teeth, about the thickness of hog's bristles, and of equal 
thickness throughout their length. The grinding, or cutting 
surfaces of the front, second, and third rows, in both jaws, 
are divided into three points. The two inner rows are pointed, 
and bent a little backward. 

The stomach was empty, so that I had not an opportunity 
of ascertaining its food. The intestinal canal was long, like 
that of fish which feed on vegetables ; and the oesophagus was 
thick set with pyramidal bodies, like the oesophagus of the 
turtle. 

The skeleton is very singular, many of the bones having tu- 
mours, which, in the first fish I saw, I supposed to be exostoses 
arising from disease ; but on dissecting a second, found the 
corresponding bones had exactly the same tumours, and the 
fishermen informed me they were always found in this fish ; 
I therefore conclude them to be natural to it. 

In Mr. Hunter's collection are two or three of these 
bones, but I never knew what fish they belonged to ; they 
were supposed to be from the back of some of the large 
rays. 

What advantage can arise from these large tumours is dif- 
ficult to say. Those on the spines of the vertebrae seem to an- 
swer no evident purpose, nor those at the origin of the dorsal, 
and anal fins. The particular form of the sternum, to which 
the ventral fins are joined, seems to be intended to give 
greater surface for the attachment of the muscles, and to in- 
crease their action. 


Philos. Trans. MD CCXC1IL Tab. V. p. 8 




Philos: Trans. MDCCXClll. Tab. VI. p.s' 



SiabfOrc. Jo. 



9 


a Species of Chcetodon. 

These tumours are spongy, and so soft as to be easily cut 
with a knife ; they were filled with oil. 

The air-bladder is very large, for the size of the fish, pro- 
bably to counteract the weight of the bony matter in the 
skeleton. 

It is generally caught near the shore, where there are sea- 
weeds, and the Malays say it is a dull swimmer. 

Tab. V. Represents the fish herein described. 

Tab. VI. The skeleton of the same. 


MDCCXCIII. 


C 


C 10 ] 


IV. Account of some Discoveries made by Mr. Galvani, of 
Bologna; with Experiments and Observations on them. In 
two Letters from Mr. Alexander Volta, F.R.S. Professor of 
Natural Philosophy in the University of Pavia, to Mr. Ti- 
berius Cavallo, F.R.S . 


Read January 31, 1793. 

Le sujet des decouvertes et des recherches, dont je vais vous 
entretenir, Monsieur, est VElectricite Animate ; sujet qui doit 
vous interesser vivement. Je ne sais si vous avez encore vu 
Pouvrage d’un professeur de Bologna, Mr. Galvani, qui a 
paru il y a a-peu-pres un an, avec ce titre ; Aloysii Gal- 
van 1 de Viribus Electricitatis in Motu Musculari Comment arius. 
Bononice, 1791, in 4 to, de 58 pages, avec quatre grandes plan- 
ches ; 011 du moins si vous en avez eu notice. II contient une 
des plus belles et des plus surprenantes decouvertes, et le germe 
de plusieurs autres. Nos journaux Italiens en ont donnd diff£- 
rents extraits, entre autres celui du Dr. Brugnatelli de Pavie, 
qui a pour titre, Giornale Fisico-medico ; auquel j’ai fourni moi- 
meme deux longs memoires, qui seront suivis de quelques au- 
tres, ayant beaucoup 6tendu les experiences, et pousse les re- 
cherches plus loin sur ce sujet. 

Or c’est une esquisse, tant de la d^couverte admirable de 
Mr. Galvani, que des progres que j'ai £t6 assez heureux de 
faire dans cette nouvelle carriere, que je vais vous tracer. 
Monsieur, dans cet £crit, que je souhaite que vous presentiez 


Mr. Volta's Account of Mr. Galvani’s Discoveries , &c. 11 

au digne President de la Societe Royale, le Chevalier Banks, 
pour etre communique, s J il le croit a propos, a cette savante 
Compagnie, comme un foible temoignage de ma reconnois- 
sance pour Thonneur qu'elle m’a fait de m'associer a son corps, 
et de mon zele et empressement a repondre a son invitation 
de lui faire part, de terns a autre, du fruit de mes recherches. 

(1.) Le Dr. Galvani ayant coupd et prepare une grenou- 
ille, de maniere que les jambes tenoient a une partie de l'dpine 
du dos, tronquee du reste du corps, uniquement par les nerfs 
cruraux mis a nud, vit qu J il s'excitoit des mouvements tres 
vifs dans ces jambes, avec des contractions spasmodiques dans 
tous les muscles, chaque fois que (ce reste d'animal, se trouvant 
place a une distance considerable du grand conducteur de la 
machine electrique, et dans certaines circonstances, que j’ex- 
pliquerai ensuite,) on tiroit de ce meme conducteur, non pas 
sur le corps de Tanimal, mais sur tout autre corps, et dans toute 
autre direction, une etincelle. Les circonstances requises 
etoient done, que Tanimal, ainsi disseque, se trouvat en contact, 
ou tres pres de quelque m6tal, ou autre bon conducteur assez 
£tendu, et mieux encore entre deux semblables conducteurs, 
dont Tun £toit tourne vers Pextremite des dites jambes, ou 
quelqu’un de ses muscles, Pautre vers Tepine, ou les nerfs : il 
4toit aussi tres avantageux, qu’un de ces conducteurs, que hau- 
teur distingue par le nom de conducteur des nerfs , et de conduc- 
teur des muscles, et preferablement ce dernier, eiit une libre com- 
munication avec le plancher. C'est dans cette position sur- 
tout, que les jambes de la grenouille preparee, comme on a 
dit, recevoient de violentes secousses, s'elanqoient et se de- 
battoient avec vivacitd k chaque etincelle du conducteur de 
la machine, quoiqu'il fut assez eloignd, et quoique la d^charge 

C 2 


12 Mr. Volta's Account of Mr. Galvani's Discoveries , 

ne se fit, ni sur le conducteur des nerfs, ni sur celui des 
muscles, mais sur un autre quelconque, pareillement 4loigne 
d'eux, et ayant tout autre communication par ou transmettre 
une telle dticharge, par exemple, sur une personne placee a 
Tangle oppose de la chambre. 

(2.) Ce phenomene etonna Mr. Galvani, peut-etre plus 
qu'il n'auroit du faire ; car enfin le pouvoir, non seulement des 
etincelles electriques lorsqiTelles frappent immediatement les 
muscles ou les nerfs d’un animal, mais d’un courant de ce 
fluide qui les traverse, de quelque maniere que ce soit, avec 
une suffisante rapidity, son grand pouvoir, dis-je, d’y exciter 
des commotions, £toit une chose assez connue ; d’ailleurs il 
etoit visible comment, dans cette experience, et dans toutes 
celles du meme genre rapport^es dans la premiere et seconde 
partie de son ouvrage, et qui sont representees dans les deux 
premieres planches de figures, sa grenouille se trouvoit eflec- 
tivement exposee a etre travers^e par un tel courant. On n’a 
qu'a se retracer Taction tres-connue des atmospheres elec- 
triques, ou ce qu’011 appelle electricite de pression ; par laquelle 
le fluide des corps deferents, ploughs dans la sphere d ’activity 
d’un corps electris^ quelconque, est pouss£ et deplacti, en rai- 
son de la force, et de Tetendu, de cette sphere, et entretenu en 
cet 4tat de deplacement taut que l’electricite dans le corps 
dominant subsiste, laquelle ot£e il revient a sa place des en- 
droits eloignes, peu-a-peu si elle se dissipe petit a petit, et en 
un instant si on la detruit instantanement, en dechargeant 
tout d’un coup le corps qui en est revetu. (Test done ce 
courant de retour, ce reflux de fluide electrique dans les corps 
deferents contigus a la grenouille, ou proches d’elle, son pas- 
sage brusque du conducteur des muscles au conducteur des 


with Experiments and Observations on them. 13 

nerfs, ou vice versa, a travers son corps, surtout lorsqu’un tel 
courant est resserre dans le canal unique et etroit des nerfs, 
qui excite les spasmes et les mouvements dans les experiences 
dont il est ici question. Mr. Galvani, qui semble n’avoir pas 
assez reflechi a cette action des atmospheres electriques, et 
qui ne connoissoit pas encore la prodigieuse sensibilite de sa 
grenouille, singulierement preparee de la maniere susdite, 
(je dirai ici, que je Tai trouv^e a-peu-pres egale dans tous les 
autres petits animaux, comme lezards, salamandres, souris) 
fut extremement frappe d’un tel effet, qui ne paroitra pas si 
merveilleux a d'autres physiciens. Ce fut pourtant le pre- 
mier pas, qui le conduisit a la belle et grande decouverte 
d'une electricite animate proprement dite, appartenante non 
seulement aux grenouilles, et a d'autres animaux a sang froid, 
mais aussi-bien a tous les animaux a sang chaud, quadrupedes, 
oiseaux, &c. ; decouverte qui fait le sujet de la troisieme partie 
de son ouvrage, sujet absolument neuf, et tres interessant. 
C'est ainsi quhl nous a ouvert un champ tres vaste, dans le- 
quel nous nous proposons d'entrer, et de poursuivre les re- 
cherches, apres que nous nous serons arrete encore un peu sur 
ces experiences preliminaires qui concernent Faction de Telec- 
tricit£ ariificielle, ou etrangere, sur les fibres nerveuses et mus- 
culaires. 

(3.) Ce fut le hazard qui presenta a Mr. Galvani le ph6- 
nomene que nous venous de decrire, et dont il fut £tonne, je 
le repute, plus qufil n'auroit du etre. Cependant qui est ce qui 
auroit cru, qu’un courant 61ectrique, foible au point de ne pou- 
voir etre rendu sensible par les electrometres les plus delicats, fut 
capable d'affecter si puissamment les organes chun animal, et 
d'exciter dans ses membres, d£coup£s une ou plusieurs heures 


*4 Mr . Volta's Account of Mr. Galvani's Discoveries , 

avant, des mouvements, tels que 1 animal vivant n^en produit 
pas de plus forts, comme d'elancer vigoureusement les jambes, 
de sauter, &c. pour ne rien dire des convulsions toniques les 
plus violentes ? Or tel est le courant qui envahit le petit ani- 
mal couche, par exemple, sur la table, aupres de quelque me- 
tal, ou entre deux bons conducteurs non isolEs, lorsquune 
personne tire du grand conducteur Electrique, suspendu plu- 
sieurs pieds au dessus, une mediocre Etincelle, et dirige la dE- 
charge par une tout autre voie. 

(4.) Je dis mediocre ; car si elle est bien forte, et si la dis- 
tance de ce conducteur, puissamment ElectrisE et volumineux, 
aux corps posEs sur la table n'est pas fort grande, il paroitra 
des petites Etincelles dans les interstices de ces corps sur- 
tout metalliques, et la meme ou la grenouille fait un anneau de 
communication entr'eux ; Etincelles produites evidemment 
par ce fluide Electrique de retour, dont nous avons parlE ci- 
dessus. (sect. 2.) Ou, si la chose n'arrive pas a ce point, au 
lieu des Etincelles, on pourra observer des mouvements assez 
marquEs de quelques Electrometres placEs sur la meme table, 
et aux memes endroits. Or dans ce cas, ou les Electrometres 
donnent des signes, et beaucoup plus dans Tautre, ou l'on ob- 
tient les susdites Etincelles, on pourra observer que meme une 
grenouille entiere et intacte, ou un autre petit animal quel- 
conque, un lezard, un souris, un moineau, sont saisis de fortes 
convulsions dans tous leurs membres, surtout dans les jambes^ 
qui s'Elancent avec vivacitE, si le passage du fluide Electrique 
(le courant de retour) suit la direction de ces memes jambes 
dun bout a Tautre. Jusques-la point de merveille ; la sur- 
prise est dans le cas ou le courant Electrique n'Etant plus sen- 
sible, pas meme aux Electrometres les plus delicats, il excite 


with 'Experiments and Observations on them. 15 

encore les memes convulsions, les memes mouvements et de- 
bats, si non dans la grenouille entiere, au moins dans ses mem- 
bres disseques et prepares a la maniere de Mr. Galvanl 

(5.) Je me suis appliqu£, avec quelque attention, a deter- 
miner quelle 6toit la moindre force electrique requise a pro- 
duire ces effets, aussi bien dans une grenouille intacte et pleine 
de vie, que dans une dissequee et prepare a la dite maniere ; 
ce que Mr. Galvan 1 avoit omis de faire. J'ai choisi la gre- 
nouille de preference a tout autre animal, a cause qu’elle est 
douee d'une vitalite tres-durable, et qu'il est fort aise de la 
preparer. Au reste j'ai aussi fait des epreuves sur d'autres 
petits animaux, dans cette vue, et avec un succes a-peu-pres 
£gal. Pour bien ^valuer la force du courant electrique, j’ai 
cru devoir soumettre Panimal destine aux experiences de ce 
genre, non pas aux courants de retour occasionn^s par les at- 
mospheres, (sect. 2.) mais aux d^charges tdectriques directes, 
tantot d'un simple conducteur, tantot d'une bouteille de Leyde, 
et en sorte que tout le courant dut traverser le corps de Pani- 
mal. A cet effet j'avois soin de le tenir isol£ d'une maniere 
ou de Pautre, et le plus souvent en l'attachant, par des epin- 
gles, a deux plateaux de bois tendre, port^s par des colonnes. 
de verre. 

(6.) J ai done trouv£, que pour la grenouille vivante et en- 
tiere il suffisoit de Pelectricite d'un simple conducteur, de moy- 
enne grandeur, quand elle arrivoit seulement a pouvoir donner 
une tres foible £tincelle, et a elever de cinq a six degr^s Pelec- 
trometre de Henly. Que si je me servois d'une bouteille de 
Leyde, aussi de moyenne grandeur, une charge de celle-ci 
beaucoup plus foible produisoit l'effet, telle, par exemple, que 
ne donnant pas la moindre etincelle, et n'^tant aucunement 


i6’ Mr. Volta's Account of Mr. Galvani’s Discoveries, 

sensible au quadrant-Electrometre, l'etoit a peine a un eleo 
trometre de Cavallo au point d'Ecarter d'une ligne environ 
ses petits pendules. 

(7.) Cela, comrne je viens de montrer, pour une grenouille 
entiere et intacte ; car pour une dissEquEe et prEparEe en dif- 
ferentes manieres, et sur-tout a la fa^on de Galvani, oil les 
jambes tiennent a repine dorsale par les seuls nerfs cruraux, 
une electricite beaucoup plus foible encore, soit du conducteur, 
soit de la bouteille de Leyde, (le fluide Etant oblige d'enfiler ce 
passage etroit des nerfs,) ne manquoit pas d’exciter les convul- 
sions, &c. Oui une electricite quarante 011 cinquante fois plus 
foible, comrne une charge de la bouteille absolument imper- 
ceptible au dit Electrometre de Cavallo, et meme a celui 
extremement delicat de Bennet ; une charge, que je ne pou- 
vois rendre sensible qif a Taide de mon condensateur, et que je 
crois pouvoir evaluer a cinq ou six centiemes de degrE de 
I’Electrometre de Cavallo. 

(8.) Voila done, dans les jambes de la grenouille attachees a 
Bepine du dos uniquement par ses nerfs bien dEpouillEs, une 
nouvelle espece d’electrometre ; puisque des charges Elec- 
triques qui, ne donnant aucun signe a ceux-ci, paroitroient 
nulles, en donnent de si marques par ce nouveau moyen, par 
un tel electrometre animal , si on peut Tappeller ainsi. 

(9.) Lorsqu'on a vu comment une grenouille ainsi prEparEe 
se ressent, et est saisie de fortes convulsions par une electri- 
cite extremement foible, par un courant de fluide imper- 
ceptible, on ne doit surement plus etre surpris, qifelle se de- 
batte de meme lorsqu’un corps quelconque decharge tout d'un 
coup le grand conducteur de la machine electrique, et fait 
qu'un autre courant de fluide Electrique, grand ou petit, du 


17 


with Experiments and Observations on them. 

fluide ci-devant deplace dans Jes corps deferents aupres de la 
grenouille, et qui se rEtablit, comme on a explique plus haut, 
(sect. 2) passe rapidement a tracers ses nerfs. Supposons que 
ce courant de retour soit a peine equivalent a celui que lance 
directement un conducteur suffisamment volumineux, avec une 
Electricity non Etincellante, et presqid insensible jusqu’a l’elec- 
trometre de Cavallo, ou une petite bouteille de Leyde, 
chargEe a peine un dixieme de degre de ce meme Electro- 
metre ; supposons, dis-je, que le courant Electrique ne soit pas 
plus fort que cela, il suffit encore, comme mes experiences, 
rapportEes ci-dessus, (sect. 6 . et 7.) font voir, pour exciter les 
mouvements dont il s’agit. 

(10.) Mais si on ne doit plus etre surpris, apres ces expE- 
riences, de celles de Mr. Galvani decritesdans la premiere et 
seconde partie de son ouvrage, comment s'empecher de l’etre 
de celles tout-a-fait nouvelles et merveilleuses qu'il rapporte 
dans la troisieme ? Par lesquelles il obtint les memes convul- 
sions et mouvements violents des membres, sans avoir recours 
a aucune electricite artificielle, ou excitation etrangere, par 
la seule application d’un arc conducteur quelconque, dont un 
bout touchat aux muscles, et l'autre aux nerfs ou a l’epine de 
la grenouille, preparee de la maniere decrite. Cet arc con- 
ducteur pouvoit etre ou entierement metallique, ou partie me- 
tallique partie d’autres corps de la classe des deferents, comme 
d’eau, d'une ou plusieurs personnes, &c. Meme les bois, les mu- 
railles, le plancher, pouvoient entrer dans le circuit, pourvu 
qu'ils ne fussent pas trop secs ; il n'y a\ oit que Tinterposition 
des corps cohibents, comme verre, resines, soye, qui empechat 
Peffet. Les mauvais conducteurs cependant ne servoient pas 
si bien, et seulement pour les premiers moments apres la 

MDCCXCIII. D 


i 8 Mr. Volta's Account of Mr. Galvani' s Discoveries, 

preparation de la grenouille, tant que les forces vitales se 
soutenoient en pleine vigueur; apres quoi il n'y avoit plus 
que les bons conducteurs qu'on put employer avec succes, et 
bientot on ne pouvoit rdussir qu'avec les excellents, c'est a 
dire, avec des arcs conducteurs entierement mdtalliques. II 
trouva au surplus un grand avantage a appliquer une espece 
d'armure metallique a cette portion d'dpine qu'il laissoit at- 
tachde aux nerfs cruraux, et aux nerfs eux-memes, et surtout 
a revetir cette partie d'une feuille mince d'etain ou de plomb. 

(11.) Mr. Galvani ne s'arreta pas, dans ces experiences 
vraiment etonnantes, aux grenouilles ; il les etendit avec sue- 
ces, non seulement a plusieurs autres animaux a sang-froid, 
mais aussi aux quadrupedes, et aux oiseaux ; dans lesquels il 
obtint les memes resultats,moyennant les memes preparations ; 
qui consistoient a degager de ses enveloppes un des principaux 
nerfs, la ou il s'implante dans un membre susceptible de 
mouvement, a armer ce nerf de quelque lame ou feuille me- 
tallique, et a etablir une communication, a Taide d'un arc 
conducteur, de cette armure du nerf aux muscles dependants. 

(12.) C'est ainsi qu'il decouvrit heureusement, et nous de- 
mon tra, de la maniere la plus evidente, Inexistence d'une ve- 
ritable electricite animale dans tous, ou presque tous les ani- 
maux. Il paroit prouvd en effet par ses experiences, que le 
fluide electrique tend sans cesse a passer d'une partie a Tautre 
du corp organique vivant, et meme des membres tronques, 
tant qu J il y subsiste un reste de vitality ; qu'il tend a passer 
des nerfs aux muscles^ ou vice versa, et que les mouvements 
musculaires sont dus a une semblable transfusion, plus ou 
moins rapide. En veritd il semble qu'on ne peut rien opposer 
a cela, ni a la fa^on dont Mr. Galvani expliquela chose, par 


with Experiments and Observations on them. 19 

une espece de decharge semblable a celle de la bouteille de 
Leyde. Cependant an grand nombre de nouvelles experiences, 
que j'ai faites sur ce sujet, font voir qu'il y a bien des restric- 
tions a faire, tant a la chose, qu'aux consequences que hauteur 
en a tirees ; en meme terns qu'elles dtendent beaucoup les 
phenomenes attribues a cette electricite animate, et nous la re- 
presented dans un grand nombre de circonstances et de 
combinaisons nouvelles. 

(13.) Mr. Galvani, suivant l'idee qu'il s'est fait, d'apres 
ses experiences, et pour suivre, en tout point, Tanalogie de la 
bouteille de Leyde et de Tare conducteur, pretend qu'il y ait 
naturellement un exces de fluide electrique dans le nerf, ou 
dans Tinterieur du muscle, et un defaut correspondant dans 
Texterieur, ou vice versa ; et suppose consdquemment qu'un bout 
de cet arc doit communiquer au nerf, qu'il regarde comme 
le fil conducteur, ou crochet de la bouteille ; Tautre bout a la- 
face exterieure du muscle. Toutes les figures de la troisieme 
et quatrieme planche, et toutes ses explications reviennent 
a cela. Mais s'il avoit un peu plus varie les experiences, 
comme j'ai fait, il auroit vu que ce double contact du nerf et 
du muscle, ce circuit quhl imagine, n'est pas toujours n£ces- 
saire. II auroit trouvd, ce que j'ai trouvd, qu'on peut exciter les 
memes convulsions, les memes mouvements, dans les jambes, 
et autres membres des grenouilles, et de tout autre animal, 
par des attouchements mdtalliques, soit a deux parties du 
nerf seul, soit a deux muscles, et meme a differents points 
d’un seul et simple muscle. 

( 14. ) II est vrai qu'on ne reussit pas, a beaucoup pres, si bien 
de cette maniere que de l'autre, et qu'il faut, dans ce cas, 
avoir recours a un artifice, dont nous aurons occ asion de parler 

D 2 


so Mr. Volta's Account of Mr. Galvani's Discoveries, 

plus au long, et qui consiste a employer deux metaux dif- 
ferents ; artifice qui n'est pas absolument necessaire lorsqu'on 
expErimente suivant le procede de Galvani, decrit ci-dessus, 
(sect. 10. et 11.) du moins tant que la vitalite dans l'animal, 
ou dans ses membres coupes, se soutient en pleine vigueur ; 
mais enfin, puisque avec des armures de differents metaux ap- 
pliquEes, soit aux nerfs seuls, soit aux seuls muscles, on vient 
a bout d’exciter les contractions dans ceux-ci, et les mouve- 
ments des membres, on doit conclure que s’il y a des cas (ce 
qui pourroit bien encore paroitre douteux) ou la pretendue 
decharge entre nerf et muscle (sect. 12. et 13.) est cause des 
mouvements musculaires, il y a bien aussi des circonstances, 
et plus frequentes, ou Ton obtient les memes mouvements, 
par un tout autre jeu, par line tout autre circulation, du fluide 
Electrique. 

(15. ) Oui c'est un tout autre jeu du fluide Electrique, dont 
on doit dire plutot qu'on trouble l'equilibre, que de le retablir, 
en ce qu'il coule d'une partie a Tautre du nerf, du muscle, &c. 
tant interieurement par leurs fibres conductrices, qu'extEri- 
eurement par la voie des conducteurs metalliques appliquees, 
non pas en consequence d'un exces ou defaut respectif, mais 
par une action propre de ces memes metaux, lorsque ceux-ci 
sont de differente espece. C'est ainsi que j'ai d^couvert une 
nouvelle loi, qui n'est pas tant une loi d'electricite animale, 
qu'une loi d'electricite commune ; a laquelle on doit attribuer 
la plupart des phenomenes, qui paroissoient, d'apres les expe- 
riences de Galvani, et d'apres plusieurs autres quej'avois faites 
moi-meme a la suite de celles-la, appartenir a une veritable 
6lectricite animale spontanee, et qui n'en sont pas ; ce sont re- 
ellement des effets d’une Electricity artificielle tres foible, qui 


21 


with Experiments and Observations on them. 

s'excite d'une maniere dont on ne s'Etoit pas doutE, par la 
simple application de deux armures de differents metaux, 
comme j'ai deja indiquE, et que j'expliquerai mieux ailleurs. 

(16.) Je dois dire ici, qu'a la decouverte de cette loi nou- 
velle, de cette electricite artificielle jusqu'a present inconnue, 
je me defiai d'abord de tout ce qui m'avoit pam demontrer 
une Electricite animale naturelle, dans le sens propre, et que 
j'etois sur le point de revenir de cette idee. Mais repassant, 
avec un examen reflechi, tous les phenomenes, et repetant les 
experiences sous ce nouveau point de vue, je trouvai enfin 
que quelques unes soutiennent encore cet examen, (celles, par 
exemple, oil Ton n'a pas besoin d'armures diflferentes, ni meme 
d'armure quelconque, un simple fil metallique, ou tout autre 
corps dEfErent, faisant office d'arc conducteur entre le nerf 
isolE et un des muscles dEpendants, pouvant exciter dans 
ceux-ci les convulsions), (sect. 10, &c.) et qu'ainsi TElec- 
tricitE animale naturelle et proprement organique subsiste, et 
ne peut pas etre renversEe entierement. Les phEnomenes qui 
TEtablissent, quoique beaucoup plus limitEs, ne laissent pas que 
d'etre demonstratifs, comme je viens d'indiquer, et comme on 
verra mieux dans la suite. 

(17.) Ce qu'on trouvera peut-etre plus desagrEable, c'est 
qu'il faut aussi renfermer en des limites plus Etroits son em- 
pire dans TEconomie animale, et renoncer aux plus belles 
idEes qu'on avoit con9ues, et qui paroissoient nous mener a 
expliquer clairement tous les mouvements des muscles. Mes 
expEriences, variEes de toutes les manieres possibles, mon- 
trent que le mouvement du fluide Electrique, excitE dans les 
organes, n'agit point immEdiatement sur les muscles ; qu'il ne 
fait qu'exciter les nerfs, et que ceux-ci, mis en action, excitent 


22 Mr. Volta's Account of Mr. Galvani's Discoveries , 

a leur tour les muscles. Quelle soit cette action des nerfs ; 
comment elle se propage d'une de ses parties aux autres; com- 
ment elle passe aux muscles, et comment il en resulte le 
mouvement de ces derniers ; ce sont encore des problemes, pour 
l’explication desquels nous n'en sommes pas plus avances 
qu'avant la decouverte dont il s'agit. 

(18.) Je viens maintenant aux experiences qui prouvent 
toutes les assertions que j’ai avancdes dans ces derniers para- 
graphes. Dans la foule qui se presente j’en choisirai quelques 
unes seulement, celles qui me paroissent mieux etablir cer- 
tains principes, la plupart nouveaux et differents de ceux 
adopts par Mr. Galvani. Mais disons premierement encore 
un mot des experiences de cet auteur. Je ne sais s’il en a fait 
d'autres, mais celles dont il nous rend compte dans son ouvrage 
sont renfermdes dans un cerc.le trop etroit ; il s'agit toujours 
de decouvrir et isoler les nerfs, et d'etablir une communica- 
tion, de corps conducteurs de Telectricite, entre ces nerfs et les 
muscles qui en dependent, (comme on voit dans toutes les fi- 
gures des quatres planches jointes a ce meme ouvrage) 
lorsqu'on se propose d'exciter les convulsions et mouvements 
de ces muscles, par Taction du fluide electrique. Il suppose 
done, dans tous les cas, et il s'explique la dessus assez clairement, 
que la transfusion du fluide electrique produite, soit par Telec- 
tricite artificielle, soit par Telectricite animale naturelle, doive 
se faire des nerfs aux muscles, ou vice versa ; que ces deux 
termes au moins y doivent etre compris, pour que les mouve- 
ments musculaires ayent lieu ; et vraiment toutes les expe- 
riences qu'il nous decrit semblent prouver cela. Mais e'est 
qu’elles roulent, comme j'ai deja dit, dans ce cercle trop etroit, 
dont il n'est jamais, ou presque jamais, sorti. En variant les 


23 


with Experiments and Observations on them. 

experiences de ce genre de plusieurs manieres, j'ai fait voir, 
que ni Tune ni Tautre de ces conditions, savoir, de decouvrir et 
isoler les nerfs, et de toucher simultanement ceux-ci et les 
muscles, pour procurer la pr^tendue decharge, sont absolu- 
ment necessaires (sect 13.). II suffit, lorsqu'on a par exemple 
decouvert le nerf ischiatique a un chien, a un agneau, & c. de 
faire passer un courant electrique d’une partie de ce nerf a 
une autre, meme prochaine, en laissant tout le reste intact et 
libre, et intacte encore plus toute la jambe ; il suffit, dis-je, de 
cela pour voir excites dans cette jambe les convulsions et les 
mouvements les plus forts ; et cela, soit qu’on employe une 
electricity artificielle etrangere, soit qu J on mette en mouve- 
ment le fluide dlectrique inherent au nerf lui-meme. Voici 
de quelle maniereje fais ces experiences. 

(19.) Experience A. Je serre, avec des pincettes, le nerf 
ischiatique un peu au dessus de son insertion dans la cuisse, et 
j'applique, quelques lignes plus haut, une piece de monnoye, ou 
une autre lame metallique, sur ce meme nerf, detache soigneuse- 
ment de ses adhdrences, et soutenu par un fil, ou appuye a 
une plaque de verre, a un baton de cire d'Espagne, ou de 
bois sec, ou a tout autre corps mauvais conducteur. Alors 
appuyant le ventre dffine bouteille de Leyde, tres foiblement 
chargee, aux dites pincettes, je porte le crochet en contact de 
Tautre lame metallique ; et voila que la decharge qui se fait, 
quand meme elle n’est pas assez forte pour donner la moindre 
ytincelle, fait entrer en convulsion tous les muscles de la cuisse 
et de la jambe, qui est secou^e et stance avec plus ou moins 
d'impetuosite. Et cependant toute cette jambe, et une partie 
meme du nerf qui en deborde, se trouvoient, comme on voit, 
hors la route que le fluide dlectrique a parcouru dans son 


24< Mr. Volta's Account of Mr. Galvani's Discoveries, 

trajet, de sorte qu'une petite partie seulement du nerf a pa 
£tre irritee ; cela neanmoins a suffi pour occasionner la con- 
traction des muscles. 

(20.) Experience B. II en est de meine, cest-a-dire de 
semblables convulsions et mouvements de la jambe ont lieu, 
sans avoir recours a une ^lectricite etrangere, par la d^charge 
qui se fait, en certaine maniere naturellement, lorsqu’ayant ap- 
plique, comme ci-dessus, les memes pincettes, ou une lame 
d’argent, a une partie du nerf, et une lame de tout autre m£tal, 
et surtout detain ou de plomb, a une autre partie, on les fait 
simplement communiquer entr'elles, soit par un contact im- 
mediat, ou par rentremise d J une troisieme piece de m£tal, 
qui fasse Toffice d'arc conducteur. 

(si.) Or done voila les memes effets, des convulsions et 
mouvements musculaires les plus vifs, sans que la decharge de 
fluide dlectrique se fasse entre les nerfs et les muscles, comme 
Mr. Galvani suppose toujours; et sans quhl soit besoin 
qu'un bout de Tare conducteur communique aux uns, et fautre 
bout aux autres. Mais aussi fautre condition, de depouiller 
un nerf quelconque et le mettre a nud, n'est pas plus requise, 
comme les experiences suivantes vont montrer. 

Experience C. Eapplique les armures, oil lames de dif- 
ferents metaux (e'est cette difference des armures qui est es- 
sentielle) (sect. 14. et 15.) a une grenouille toute entiere et 
vivante, revetue meme de sa peau, en un mot intacte : je 
colle, par exemple, une feuille mince d'etain sur son dos, ou sur 
les reins, et je pose une piece de monnoye d J argent sous ses 
cuisses, ou sous son ventre, fy comprimant un peu ; cela fait, 
j'avance cette monnoye, en la glissant, jusqifau contact de la 
feuille detain, ou bien j'etablis une communication entre ces 


with 'Experiments and Observations on them. 23 

deux armures, moyennant un fil d'archal, ou une autre piece 
de metal quelconque ; et voila qu J il s J excite des convulsions 
spasmodiques dans tous les muscles du ventre, des cuisses, du 
dos, avec de violentes secousses des jambes, une contraction 
et courbure de Tepine, &c. lesquelles convulsions et spasmes. 
quoique presqu'universelles, sont cependant plus marques 
dans les membres et muscles qui touchent, ou avoisinent, les 
armures, et plus encore dans ceux qui dependent des princi- 
paux nerfs proches eux-m£mes aux dites armures. 

(22.) Ces experiences reussissent dans quelques autres ani- 
maux ; dans les poissons, et dans les anguilles sur-tout, aux- 
quels il iTest pas necessaire d'oter la peau, quoiqif elle ne laisse 
pas que d’emp^cher un peu Taction. (Test pourquoi en la 
leur otant, au moins en partie, particulierement a la gre- 
nouille, on obtient plus surement les effets, et on les obtient 
beaucoup plus grands. On gagne encore, a cet egard, si on 
coupe la tete a la grenouille, et si on finit de la tuer en lui en- 
fon9ant une grosse 6pingle dans la moelle epiniere ; on ex- 
cite alors, par le moyen decrit des armures metalliques dif- 
fdrentes, des mouvements plus forts, ou qui paroissent au 
moins plus marquds, parce qudls ne se confondent pas avec 
les autres mouvements que Tanimal se donne etant en vie. 

(23.) S’il est avantageux, comme on vient de voir, d'oter la 
peau aux grenouilles, quoique fort mince et assez humide, il 
Test beaucoup plus, et meme necessaire, de Toter a presque 
tous les autres animaux, lezards, salamandres, serpents, tor- 
tues, et sur-tout aux quadrupedes, et aux oiseaux, fournis 
d'une peau plus seche, et beaucoup plus epaisse, pour reussir 
dans ces experiences. Voici done comment je nTy prends. 

Experience D. J’attache a une table, au moyen de 
mdccxciii. E 


q 6 Mr. Volta's Account of Mr. Galvani's Discoveries, 

quelques grosses epingles, un lezard, une souris, un poulet, 
&c. et en faisant une incision a la peau et aux autres inte- 
guments, jusqu'a la chair nue, sur le dos de l’animal ainsi 
assujetti, je renverse les integuments des deux cotds; j'en fais 
autant a la cuisse ou a la jambe, apres quoi j'applique les 
deux armures aux endroits ddnu6s, ici la feuille detain, la la 
cuiller ou la piece de monnoye. Alors, toutes les fois que je 
fais communiquer entr'elles ces deux armures, il s'excite de 
fortes contractions dans les muscles adjacents, et sur-tout dans 
ceux de la cuisse et de la jambe, qui remue et se debat tres- 
fort. Ces secousses sont beaucoup plus violentes selon que la 
feuille detain se trouve appliquee plus pres du nerf iscbiatique, 
et la lame d'argent mieux appliquee au muscle qu'on appelle 
gluteus, ou a l’autre dit gastrocnemius, et toujours plus si on va 
jusqu'a decouvrir ce meme nerf, et a le revetir lui-meme de 
la feuille detain; si, le laissant attache seulement aux muscles 
dans lesquels il s'implante, on lui ote tout autre adherence; si 
enfin on detache tout le membre du reste du corps, avec son 
nerf pendant, et on Tassiijettit seul aux experiences. 

Je suis, &c. 

A. VOLTA, 


Septembre 13, 1792. 


with ’Experiments and Observations on them. 


27 


Second Letter. 

(24.) AU reste on comprend bien que ce queje viens ds 
faire observer, par rapport au nerf ischiatique et a la jambe, a 
lieu pour le nerf brachial et le bras, et pour tout autre nerf 
relativeinent aux muscles et membres rdgis par ces nerfs. 

(25.) Ces dernieres preparations reviennent a celles de Mr. 
Galvan 1 ; et elles prouvent bien qu'il est avantageux de 
mettre a decouvert les nerfs, et plus encore de les detacher 
tout-au-tour ; mais nullement que ce soit une condition ne- 
cessaire, puisqu’on ne manque pas d'obtenir les memes con- 
vulsions et mouvements des membres lorsqu’on decouvre sim- 
plement les muscles, et qu'on laisse tours les nerfs enveloppes et 
caches sous eux dans l’etat nature!, comme toutes mes autres 
experiences ci-devant rapportdes (sect. 21. 22. 23.) font voir. 

(2b.) Apres ces essais sur des reptiles, sur des oiseaux, et 
sur de petits quadrupedes, je procedai a d'autres animaux 
plus grands, lapins, chiens, agneaux, boeufs ; et non seulement 
je parvins a produire de semblables eflets par toutes les ma- 
nieres ddcrites, mais a en obtenir de plus marques et plus 
durables, a raison que la chaleur vitale se soutenoit dans ces 
grands animaux, et dans leurs membres, plus long-terns. Car 
je ne dois pas n£gliger de dire, que si dans la plupart des ani- 
maux a sang froid, et particulierement dans les grenouilles, la 
vitalite subsiste dans les membres tronques plusieurs heures, 
cette vitalite qui les rend si sensibles a la plus foible irrita- 
tion electrique, elle ne dure gueres que quelques minutes 

E 2 


28 Mr. Volta's Account of Mr. Galvani's Discoveries, 

dans les membres decoupes des animaux a sang chaud, et 
disparoit communement avant que toute cette chaleur animale 
soit dissipee. 

(27.) Ayant eu un tel succes de mes experiences sur des 
animaux grands et petits de toute espece, tantot vivants et 
dans toute leur int^grite, tantot ecorches, quelquefois deca- 
pites, et disseques de differentes manieres, et dans chacun 
de leurs gros membres tronques, et presque toujours sans cette 
preparation requise par Mr. Galvan i, c'est a dire, sans 
mettre a decouvert les nerfs, je voulus aller plus loin, et es- 
sayer sur de petits membres, sur un seul muscle, et sur de 
petits morceaux de muscles ; et le nouveau succes que j'en ai 
eu m’a conduit a d'autres decouvertes, que j'exposerai bientot, 
apres avoir d^crit quelques unes de ces experiences. 

(28.) Experience E. J'ai coup6 tantot unejambe avec la 
cuisse, tantot la jambe seule, tantot une moitie ou un quart 
de jambe, a une grenouille ; et ayant applique, a l'ordinaire, a 
une partie de la piece couple la feuille detain, et a une autre 
partie la lame d'argent, et fait communiquer entr’elles ces 
armures, j'obtins toujours des convulsions et mouvements. 
J'en ai detache un seul muscle, par exemple le gluteus ou le 
gastrocnemius ; d'autres fois je n'en ai pris qu'un morceau pas 
plus gros qu'un grain d'orge ; mdmes effets, savoir, des con- 
tractions tres vives et spasmodiques de ces muscles, ou de ces 
morceaux de muscles, moyennant Tartifice de deux armures 
differentes, &c. 

Experience F. J'ai rep6t£ les memes experiences sur une 
jambe, une moitie et un tiers de jambe, sur un seul muscle, et 
un fragment de muscle, de poulet, et d'autres oiseaux ; sur une 


with Experiments and Observations on them. 2 g 

tranche du gluteus d\m lapin, d J un agneau, &c. et j J ai eu les 
memes effets tout le terns que les chairs ont conserve une 
chaleur sensible, (sect. 26.) 

(2 9.) Ainsi done on excite des contractions tres fortes dans 
les muscles des animaux a sang chaud, comme a sang froid, 
et dans toutes les parties coupees des muscles ; et on les ex- 
cite par le simple artifice des armures metalliques differentes, 
appliquees au muscle lui-meme, sans aucune preparation des 
nerfs, meme sans decouvrir ceux-ci. Ailleurs nous avons vu 
qu'on les excite egalement, et par le meme moyen des ar- 
mures appliquees a deux parties voisines du nerf seul, (sect. 
19. et 20. Experience A. et B.) d’ou j'ai raison de conclure 
qufil n'est pas du tout necessaire qufil se fasse une decharge 
de fluide electrique entre nerf et muscle, 011 qu'il s'en trans- 
porte de l'interieur a Texterieur de ce dernier par le nerf et 
par 1 J arc conducteur, comme Mr. Galvan 1 suppose, ou vice 
versa ; et qufil n"y a aucune comparaison a faire du muscle 
avec la bouteille de Leyde et sa discharge, dans les expe- 
riences dont il s^agit ici. Qu(y a-t-il en effet qui resemble, et 
qu'on puisse expliquer analogiquement a la bouteille, lorsque 
les deux lames de metal, auxquelles arrivent les deux bouts de 
Tare conducteur, se trouvent appliquees tres pres l’une de 
Bautre a Texterieur du meme nerf, (Experience A. et B.) ou sur 
Texterieur de deux muscles semblables, ou sur le meme muscle ; 
(Experience C. D. E. F.) il faut convenir qu'on feroit inu- 
tilement des efforts pour soutenir ici une analogie avec la 
bouteille de Leyde. 

(30.) Experience G. Ay ant revetu de deux feuilles, une 
d'argent Tautre detain, les deux cuisses d’une grenouille aux 
endroits precisement correspondants, on excite les contractions 


30 Mr. Volta’s Account of Mr. Galvani’s Discoveries, 

des muscles, et les mouvements ordinaires des jambes, au mo- 
ment qu’on fait communiquer par un arc conducteur ces deux 
armures. 

(31.) Est ce comme cela, je demande, que se fait la dd- 
charge de deux bouteilles de Leyde, en dtablissant une commu- 
nication entre les surfaces homologues ? Laissons done la ces 
idees de bouteille et decharge, et toute explication forcee, et 
disons simplement qu’il se fait ici, et dans les experiences ana- 
logues, un transport de fluide electrique de Tune a l’autre des 
deux parties convenablement arrnees ; transport determine, 
non par un exe'es respectif de ce fluide, qu’on lie sauroit natu- 
rellement supposer entre des parties similaires, mais par la di- 
versity de ces memes armures, qui doivent etre de differents 
metaux, comme j’ai eu soin d’indiquer deja, (sect. 20. et 21. 
Experience B. et C.) et toujours inculque dans la suite. 
En effet, 

(32.) Experience H. Si deux muscles, ou deux endroits 
d’un seul muscle, sont armds pareillement, e’est a dire, de 
deux lames d’un meme mdtal, egales aussi quant a leur 
trempe et durete, souplesse ou rigidite, quant au poli ou a la 
rudesse des superficies, et appliquees de la meme maniere, on 
aura beau les faire communiquer par un arc conducteur, il ne 
s’ensuivra aucune convulsion, aucun mouvement. 

(33.) J’avoue qu’il 11’est pas aise de concevoir comment et 
pourquoi la simple application de deux armures dissemblables, 
je veux dire de deux differents mdtaux, a deux parties simi- 
laires de l’animal, et meme a des points tres proches les uns 
des autres d’un muscle quelconque, trouble 1’equilibre du 
fluide electrique, et, le tirant de son repos etde son inaction, le 
sollicite de passer incessamment d’un endroit a l’autre ; lequel 


with Experiments and Observations on them. 31 

transflux a lieu sitot qu’011 etablit un arc conducteur entre ces 
deux armures dissemblables, et continue tout le terns que 
cette communication subsiste. Mais concevable ou non, qu’en 
soit la cause, c'est un fait que les experiences deja rapport^es 
prouvent assez, et qui sera confirme par beaucoup d’autres ; a 
la suite desquelles je tacherai d’en donner quelqu’explication. 
C'est un fait qu’on doit ajouter a ce que nous connoissions 
deja en electricite ; un fait qui doit surement paroitre ex- 
traordinaire, et difficile a concilier avec les lois commune- 
ment dtablies. C’est veritablement une nouvelle loi bien sin- 
guliere, que j J ai decouverte ; une loi qui n’appartient pas pro- 
prement a Telectricite animale, mais a T^lectricite commune, 
puisque ce transflux de fluide 61 ectrique, transflux qui lflest 
pas au surplus momentane, comme seroit une decharge, mais 
continu et suivi tout le terns que la communication entre les 
deux armures subsiste, a lieu, soit que celles-ci se trouvent ap- 
pliquees aux substances animales vivantes ou mortes, ou a 
d’autres conducteurs non metalliques, mais suffisamment bons, 
comme a l’eau, ou a des corps mouilles. Mais avant que 
d'en venir aux experiences qui prouvent decidement tout ce 
que j’avance ici, je dois encore m’arreter quelque peu sur celles 
que j’ai deja rapportees. (sect. 20. — 32.) 

(34.) II paroit d’abord par celles-ci qu’on peut exciter, 
moyennant le simple artifice des armures de differents me- 
taux convenablement appliqudes, de fortes contractions dans 
tous les muscles de tous les animaux, tant qufils jouissent 
encore de quelque vitalite. Une telle conclusion seroit pour- 
tant trop generale, et l’expdrience merne, au milieu des 
preuves que j'ai si fort etendues, m J a appris qufil faut y 
mettre des restrictions, tant relativement aux classes et 


32 Mr. Volta's Account of Mr. Galvani’s Discoveries , 

genres cTanimaux, que par rapport aux differents muscles de 
chaque animal. 

(35.) Et premierement pour ce qui est des diffdrentes 
classes d’animaux ; quoiqu’il soit bien constant que tous les 
quadru pedes, les oiseaux, les poissons, les reptiles, et les amphi- 
bies, que j’ai soumis aux £preuves, presentent les phdnomenes 
decrits, il n’en est pas moins vrai que les vers en general, et 
plusieurs insectes, s’y sont refuses. J'ai essaye en vain les vers 
de terre, les sangsues, les limaces et lima^ons, les huitres, et 
diverses chenilles ; je n’y ai pas meme pu exciter des mouve- 
ments par de petites et mediocres dtincelles, et decharges, 
d’electricite artificielle. Voici de quelle maniere j’ai pro- 
cede. 

Experience I. J’ai applique la feuille d’etain, et la lame 
d’argent, a differentes parties, tant exterieures qu’interieures, 
de ces limaces, sangsues, vers de terre, &c. et le mieux qu’il m’a 
ete possible; etj’aietabli la communication de ces armures 
metalliques. tantot en approchant l’une de l’autre jusqu’au con- 
tact, tantot par l’intermede d’un autre metal faisant office 
d’arc conducteur ; mais par tous ces moyens je n’ai jamais 
pu obtenir le moindre mouvement dans aucune partie de 
leur corps. 

Experience L. J’ai affectue a travers leurs corps, isoles 
ou non isoles, des decharges de bouteille assez fortes pour ex- 
citer une mediocre dtincelle, et pour me donner une petite 
commotion, et ils n’en furent pas sensiblement affectes; point 
de mouvements ou des convulsions. 

(36.) Est-ce done que les animaux les plus imparfaits, la 
classe entiere des vers, et plusieurs insectes ne possederoient 
gueres cette sensibilite et irritabilite, cette mobilite electrique. 


tvith Experiments and Observations on them. 


33 


s'il m’est permis de dire ainsi, dont jouissent les autres ani- 
maux plus parfaits ? Je ne veux point encore tirer cette con- 
clusion generale de mes experiences, que je n'ai dtendues 
jusqu'a present qu J a un petit nombre de vers et d'insectes. 
Encore, a regard de ces derniers, je dois dire que j J ai reussi, 
sans beaucoup de difficult^, sur des ecrevisses, des scarabes, 
des sauterelles, des papillons, des mouches. II ne sera pas 
inutile que j'explique une des manieres par lesquelles je viens 
a bout avec ces animaux, difficiles d'assujettir aux experiences, 
ou par leur petitesse, ou par les ecailles dont ils sont re- 
couverts. 

Experience M. Apres avoir tranche la tete a la mouclie, 
au papillon, au scarabd, & c. je leur fend, tout au long, le corce- 
let avec un canif, ou de petits ciseaux ; et j’introduis pro- 
fond^ment dans la fente, pres du cou, un morceau de feuille 
detain, (le papier dit improprement argente est tres a 
propos) et un peu au dessous j'introduis, de meme bien avant 
dans Tint^rieur, le tranchant d’une lame d’argent, ou d’une 
petite monnoye : alors quand j’avance celle-ci jusqu’au con- 
tact de la feuille d’dtain, les jambes commencent a se plier, a 
se debattre, et les autres parties, et le tronc meme, a s'agiter. 
II est fort amusant d'exciter de cette maniere le chant d'une 
cigale, &c. 

(37.) Ainsi done j’aurois grand tort de ranger les in- 
sectes parmi les animaux destitues, comme le sont les vers 
deja indiqu^s, de la faculte electrique dont il s’agit. Tout au 
plus', si les chenilles se montrent telles, on peut dire que dans 
cet etat de larve, avant d’atteindre par leur metamorphose 
retat parfait, d'acquerir de nouveaux organes, &c. de meme 
qu'elles sont comparables aux vers a plusieurs autres egards, 

mdccxciii. F 


34 Mr. Volta^s Account of Mr. Galvanfs Discoveries , 

elles le sont aussi a celui de rdetre pas doudes de la sensibilite 
electrique. 

(38.) Enfin, s'il m’est permis de dire ici ce que je pense, 
les animaux seulement qui ont des membres bien distincts, 
des articulations, et des muscles propres pour le mouvement 
de cliacim, de ces muscles qu'on appelle flexeurs, ou eleva- 
teurs, et des nerfs propres qui les regissent, se ressentent, et 
sont saisis d J une contraction reelle et spasmodique, soit par 
de petites decharges d'dlectricite artificielle, soit par un foible 
courant de fluide occasionne par les simples armures md- 
taliiques differentes; contractions et spasmes qui entrainentle 
mouvement, et aussi ^agitation violente des dits membres. Au 
contraire les vers, et ceux d'entre les insectes qui n'ont point 
de membres assez distincts, point d'articulations proprement 
dites, ou qui manquent de ces muscles flexeurs, ou qui ne 
jouissent que d'un mouvement vermiculair, ne sont point af- 
fectes par une semblable blectricitb. (Test une tout autre 
economic animale, une tout autre mechanique pour les 
mouvements de ces animaux, un jeu qu'on a tres bien ddcou- 
vert et explique dans plusieurs especes. Voila mes idees, en- 
core un peu vagues, fondees sur quelques experiences ; c'est 
la suite de celles-ci qui doit ou les confirmer, ou les rectifier. 

(39.) A Tegard des diffbrents muscles dans le meme ani- 
mal, je suis en etat d'avancer quelque chose de plus assurd. 
Je dis done, qu'il s'en faut de beaucoup que tons les muscles 
soient susceptibles de contraction par la foible action dlec- 
trique dont il s’agit. Ilya une grande distinction a. faire par 
rapport a leur fonction dans T^conomie animale ; tons ne sont 
pas soumis a l’empire de la volontb, et prets aux mouvements 
spontanbs. Or, il riy a proprement que ceux-ci qui soient 


35 


with Experiments and Observations on them. 

capables des contractions spasmodiques, par les moyens decrits. 
Oui, il n'y a que les muscles obeissants a la volonte que j'ai 
trouves susceptibles d'irritation et de mouvement, par Taction 
de ce foible courant de fiuide dlectrique occasionne par le 
simple attouchement de deux metaux differents ; et point 
du tout les autres muscles sur lesquels la volonte iTa aucun 
pouvoir direct, comme ceux du ventricule, des intestins, &c. 
pas meme le coeur, d'ailleurs si irritable. Les muscles du dia- 
phragme cui ; (et je le devinai avant que d’en faire l epreuve) 
puisqiTils sont d’entre ceux dont les mouvements dependent 
de la volonte. 

Experience N. II est bien surprenant qu'une tranche de 
bonne chair musculaire, couple, par exemple, a la cuisse dun 
agneau egorge une demie heure ou une heure avant ; que ce 
morceau, dis-je, de muscle presqiTentierement refroidi, et 
qui ne se ressent plus de Taction d 'aucun stimulant mecha- 
nique ou chymique, soit si puissamment affecte par le fiuide 
61ectrique transmi d'une partie a Tautre, au point d’etre saisi 
de contractions spasmodiques tres fortes ; et qu’au contraire 
le coeur recemment arrache a ce meme animal, et encore tout 
chaud et tres irritable, traitd de meme, sollicite egalement 
par des armures metalliques le mieux adaptees, et 1 ’arc Con- 
ducteur qui en dtablit la communication, n'en souffre aucune 
alteration ; que ses battements lorsqu'ils sont affoiblis et lents 
ne redoublent point, et lorsqu'ils sont suspendus ou assoupis 
ne se reveillent pas, tandis que cela arrive par les plus foibles 
stimulants mechaniques, ou chymiques. 

( 40 .) Le fiuide electrique done, qui paroit etre le stimulant 
approprie aux muscles de la volontd, ne Test aucunement pour 
le cceur, et pour les autres muscles doues des meuvements 

F 2 


36 Mr. Volta's Account of Mr. Galvani's Discoveries , 

vitaux et animaux non volontaires. Mais que dira-t-on si je 
montrerois qu’il iTest pas non plus la cause immediate, ou effi- 
ciente, des mouvements des dits muscles volontaires ; que dans 
ceux-ci memes il n est encore qu'une cause mediate, entant 
que les nerfs seuls en sont directement affectes ? (Test ce que 
plusieurs experiences m'ont appris ; par lesquelles j'ai EtE 
force de renoncer aux plus belles et vastes idees. J'aimois a 
penser, avec Mr. Galvani, que le fluide Electrique mis en 
mouvement dans les organes, toutes les fois qu'il poussoit son 
courant jusqu'aux muscles, et qu'il les frappoit avec une cer- 
taine force, fit lui-meme Toffice de stimulant, et excitat Tirri- 
tabilitE qui leur est propre ; que tous les mouvements muscu- 
laires s'executassent par une semblable irruption de fluide 
Electrique dans les muscles, soit lorsqu'on employoit Telec- 
tricitE artificielle, soit lorsqu'on donnoit jeu a 1 'ElectricitE ani- 
male naturelle ; qu'enfin les mouvements memes qui se font 
naturellement dans la machine animale vivante, au moins les 
mouvements volontaires, reconnussent la meme cause, savoir. 
Taction immEdiate du fluide Electrique sur les muscles. Mais, 
je le repEte, j'ai du renoncer, non sans regret, a toutes ces 
belles idEes, par lesquelles il nous paroissoit possible d’expliquer 
les choses a merveille. Oui, il faut limiter beaucoup Taction 
de TElectricitE dans les animaux, et Tenvisager sous un autre 
point de vue, savoir, comme capable seulement d'exciter par 
elle-meme les nerfs, comme j'ai dEja indique, et comme je vais 
maintenant prouver. 

(4,1.) D'abord qu'elle puisse agir, et qu'elle agisse effective- 
ment, sur les nerfs, et que ceux-ci excitEs par elle excitent a leur 
tour les muscles dEpendants, sans mEme que le courant Elec- 
trique arrive jusqiTaux dits muscles, c'est un fait qui n'a plus 


37 


with Experiments and Observations on them. 

besom de preuves apres celles fournies par les Experiences A. 
et B. (sect. 1 g. et 20.) et meme par line experience de Mr. 
Galvani, qui fut la premiere de toutes, etborigine des autres, 
suivant son recit. On voit assez que le courant electrique, dans 
cette experience du professeur de Bologne, comme dans les 
miennes que je viens de citer, traverse une partie seulement du 
nerf crural, et pas un des muscles de la jambe ; cependant comme 
ils dependent de ce nerf, ils tombent tous en convulsion. 

(42.) Maisje vais plus avant et je soutiens, que meme dans 
les cas ou le courant electrique (on comprend bien que je 
n'entends parler que des foibles decharges artificielles, ou de 
ce courant qui a lieu par la simple application des armures 
de diff^rents metaux) frappe et p^netre les muscles suscepti- 
bles de mouvement, ce n'est pas en irritant ceux-ci imm^diate- 
ment qu'il les fait entrer en contraction, mais en stimulant 
leurs nerfs. C J est ce qu’indiquent deja mes Experiences C. et 
D. (sect. 21. et 23.) ou la feuille detain et la lame d'argent 
se trouvant appliquees immediatement aux parties musculeuses 
de Tanimal, soit entier, soit ^cartele, ce lie sont pas tant les 
muscles couverts par les deux armures metalliques qui souf- 
frent les plus violentes contractions, que ceux qui dependent 
de quelque nerf principal, auquel soit proche Tune ou Tautre 
des armures. C'est ainsi que dans la grenouille, lorsque la 
feuille d'etain est appliqude sur les reins, ou gissent a peu 
de profondeur les nerfs cruraux, les muscles des jambes sont 
saisis de fortes convulsions plus que tout autre, plus m£me 
que ceux qui touchent ou avoisinent Tautre armure, c'est a 
dire, la lame d’argent. J’ai deja fait observer la meme chose 
dans les quadrupedes, chiens, agneaux, &c. par rapport au 
nerf ischiatique, (Experience D.) et je dois ajouter seulement. 


38 Mr. Volta's Account of Mr. Galvani's Discoveries, 

que la jambe ne laisse pas d'etre sdcoude lorsque ce nerf 
n'est pas trop cachd sous les chairs et autres integuments, et 
on applique comme il faut a cet endroit une des armures ; 
quand meme on ne feroit point repondre l'autre ni au muscle 
gluteus, ni a aucun muscle de la jambe, mais a un autre quel- 
conque, pourvu qu'il ne soit pas trop eloigne. Voila encore 
pourquoi, 

Experience O. Si on applique a la grenouille, ou a d'au- 
tres petits animaux, la feuiile d'etain tout le long de 1'dpine 
du dos, d'oii sortent tous les nerfs du tronc et des membres; 
et l'autre arrnure a une autre partie quelconque, tous ces 
membres se debattept, les muscles, non seulement des jambes 
mais du ventre et du dos, souffrent des contractions spasmo- 
diques, et le tronc lui-meme se courbe et se plie en arc ; en un 
mot les convulsions sont gdnerales. L’experience est encore 
plus frappante dans un lezard que dans une grenouille, et je 
vais la decrire. 

Experience P. Ayant coupd la tete a un lezard, et de- 
couvert les muscles du dos en enlevant la peau, j’applique un 
morceau de feuiile d'etain au bout tronque, de maniere que 
cette feuiile deborde un peu et s'eleve sur les epaules, et je 
pose une monnoye d'argent sur le milieu de l'epine ; enfin 
je fais avancer, en glissant, cette monnoye jusqu'au contact de 
la dite feuiile. A l'instant les jambes remuent, la queue se 
replie tortueusement, et tout le corps agite se courbe et 
s'elance de droite a gauche, et de gauche a droite. N'est-ce 
pas a cause que la partie superieure de la moelle epiniere, 
la source principale des nerfs, est irritee ? 

(43.) On peut obtenir, par une semblable operation, a-peu- 
pres les memes effets dans une souris, un petit oiseau, &c. 


39 


with Experiments and Observations on them. 

mais il faut en oter, non seulement la premiere peau et les 
autres integuments, mais aussi de la chair, a raison que leur 
dos est plus charnu, et les principaux nerfs et la moeile se 
trouvent plus caches par cette chair, et par les os memes du 
tube vertebral. II est aise en effet de com prendre que le 
courant de fiuide electrique, occasionnd par les deux armures, 
ne penetrant qu'a une certaine profondeur les parties de l’ani- 
mal recouvertes par ces armures, ne peut guere atteindre ni 
la moeile epiniere, ni les principales branches des nerfs, qui 
entrent dans lfinterieur des membres, si les os, la chair, et 
d'autres integuments interposes ont une epaisseur consi- 
derable. On comprend aussi pourquoi dans les grands ani- 
maux, chiens, agneaux, &c. on ne reussit pas a exciter de 
cette maniere des mouvements dans tons les membres, je 
veux dire en appliquant les deux armures au dos, quoique de- 
charn6. Les gros troncs des nerfs restent encore trop caches, 
et ensevelis ; il n’y a que des branches ou ramifications qui 
gissent peu au dessous des dites armures, et ces branches 
lfiaboutissent, pour la plus-part, qu'a certaines parties ext£- 
rieures et voisines; en consequence on ne voit naitre commu- 
nement que des contractions et des palpitations superficielles 
dans tel ou tel autre muscle. Ou si par hazard tout un raem- 
bre est mis en •mouvement, c'est que le nerf qui entre dans 
son interieur, et regit ce mouvement, se trouve peu cache, 
qufil n’y a qu'un leger voile, une couche peu epaisse qui le cou- 
vre, des fibres minces seulement interposees entre lui et Tune 
ou l’autre des armures m^talliques ; comme on a pu observer 
dans les Experiences D. et suivantes, (sect. 23, &c.) ou il suf- 
fisoit, pour exciter de grands mouvements dans la jambe d'un 
chien, ou dfirn agneau, d’appliquer une des armures pres du 


40 Mr. Volta’s Account of Mr. Galvani’s Discoveries , 

nerf ischiatique, et plus on en approchoit, et plus on amincis- 
solt la couche de chair qui l’enveloppoit, plus les mouvements 
de la jambe etoient forts. 

(44.) II faut done connoitre la position des nerfs, leur direc- 
tion, &c. et il faut enlever non seulement les integuments com- 
muns, la graisse, & c. mais aussi partie de la chair qui couvre 
et enveloppe les dits nerfs, il faut amincir plus ou moins cette 
enveloppe, avant que d’y appliquer l’armure metallique, pour 
obtenir dans les grands animaux le mouvement de tel ou 
tel autre membre, outre les contractions et palpitations su- 
perficielles de quelques muscles. Il est peut-etre impossible 
d’exciter ces memes mouvements et convulsions dans tous les 
membres a la fois ; tandis que cela 11’est pas difficile dans les 
petits animaux, comme nous avons vu ci-dessus, (sect. 42. 
Experience O. et P.) en leur otant seulement la peau, ou 
partie des autres integuments ; ce qui n’est pas meme neces- 
saire pour la grenouille, a laquelle on peut laisser la peau, 
qui, 6tant extremement mince et humide, n’empeche pas par 
son interposition que le courant electrique atteigne les prin- 
cipaux nerfs, ou la moelle ^piniere. 

(45.) Mais s’il faut avoir egard a la direction des princi- 
paux nerfs, pour determiner les mouvements dans les diffe- 
rents membres, il faut aussi faire attention a la position des ar- 
mures relativement aux muscles; puisque ceux qui se trouvent 
interposes, et plus pres de l’une ou de l’autre armure, sont 
en general plus sujets a contracter des convulsions spasmo- 
diques, et sou vent aussi sont les seuls dans lesquels on les ob- 
serve ; par exemple, lorsque les armures ne repondent a aucun 
gros nerf, ou, s’il y en a, lorsqu’ils se trouvent trop enve- 
loppes et trop profondement caches. 


4 * 


xaith Experiments and Observations on them . 

(46.) Cela, et les Experiences E. F. (sect. 28.) ou un 
muscle seul, et meme un morceau de muscle, traite a Tordi- 
naire, ne laisse pas de souffrir des contractions tres fortes, 
pourroient faire croire que le fluide dlectrique produisit ces 
mouvements en irritant les fibres musculaires elles-mdmes, 
sans Tintervention des nerfs ; Taction desquels par conse- 
quent ne seroit ni primaire, ni absolument necessaire, comme 
je pretends. Mais Targument tire de ces exemples iTa aucune 
force, tant qiTon ne prouve pas que dans ces muscles, dans ces 
morceaux de muscle, il lTy ait gueres de nerfs ; puisque s’il y 
en a, (et certainement il doit y avoir, et il y a, des ramifica- 
tions nerveuses dans chaque portion sensible, j’ai presque dit 
dans chaque fibre musculaire) je puis toujours soutenir que ce 
sont ces filets nerveux, dont la substance du muscle se trouve 
parsemee, qui sont immediatement affectes par le fluide dlec- 
trique qui penetre cette meme substance ; que ce fluide de- 
ployant son action sur les nerfs extremement sensibles, action 
qui finit la, ceux-ci exercent la leur sur les muscles, &c. Je 
puis, dis-je, soutenir avec assez de vraisemblance que le fluide 
electrique iTa par lui-meme dfinfluence au phenomene des 
contractions musculaires, qu’en ce qu'il en excite les nerfs ; en 
un mot, qu’il n'en est pas la cause immediate. Une telle as- 
sertion, que les choses expliquees jusqifici rendent plus que 
probable, est prouvee directement, et de la maniere la plus 
evidente, comme je vais montrer, par plusieurs experiences 
que j'ai faites sur la langue : experiences qui nTont conduit 
a d’autres decouvertes, aussi intdressantes que curieuses. 

(47.) Etant parvenu a exciter des convulsions toniques, et les 
mouvements les plus forts, dans les muscles, et dans les mem- 
bres, non seulement des petits mais des grands animaux, sans 

MDCCXC III. G 


43 Mr. Volta's Account of Mr. Galvani's Discoveries , 

ddcouvrir aucun nerf, par la simple application des armures 
de diffdrents metaux aux muscles denues des integuments, je 
pensai bien-tot si on ne pourroit pas obtenir la meme chose 
dans Thornme. Je conyus que la chose reussiroit tres bien 
dans les membres amputes ; mais dans Thornme entier et vi- 
vant comment faire ? II auroit fallu aussi oter les integu- 
ments, faire des incisions profondes, emporter meme une 
partie des chairs aux endroits sur lesquels on alloit appliquer 
les lames metalliques, (comme j'ai fait remarquer qu'il faut 
faire souvent aux parties charnues des grands animaux). 
Heureusement il me vint dans la tete, que nous avons, dans 
la langue, un muscle nu, depourvu au moins des integuments 
epais dont sont couvertes les parties exterieures du corps, un 
muscle qui est tres mobile, et mobile a volonte. Voila done, 
me disois-je, toutes les conditions requises, pour pouvoir y 
exciter de vifs mouvements par Tartifice ordinaire des armures 
differentes. Dans cette vue je fis, sur ma propre langue, Inex- 
perience suivante. 

(48.) Experience Q. Ayant revetu la pointe de la 
langue, et une partie de sa surface superieure, dans Tetendue 
de quelques lignes, d\me feuille detain, (le papier dit argente 
est le plus a propos) j^appliquai la partie convexe d’une 
cuiller d'argent plus avant sur le plat de la langue, et en 
inclinant cette cuiller je portai sa queue jusqiTau contact 
de la feuille detain. Je nTattendois a voir tremblotter la 
langue ; et je faisois, pour cela, Texpdrience devant un miroir. 
Mais les mouvements que j’osois predire iTarriverent pas; 
et j’eus, au lieu de cela, une sensation a laquelle je ne nTat- 
tendois nullement ; ce fut un gout aigre assez fort, sur la 
pointe de la langue. 


43 


with Experiments and Observations on them . 

(49 ) f us d'abord fort surpris de cela ; mais refle- 
chissant un peu a la chose, je corpus aisement, que les 
nerfs qui aboutissent a la pointe de la langue, dtant les nerfs 
destines aux sensations du gout, et nullement aux mouve- 
ments de ce muscle flexible, il etoit tout-a-fait naturel, que 
Tirritation du fluide 6lectrique, mu par Tartifice ordinaire, y 
excitat une saveur, et pas autre chose ; et que pour exciter 
dans la langue les mouvements dont elle est susceptible, il 
faudroit appiiquer une des armures metalliques aupres de 
sa racine, oil s'implantent les nerfs destines a ces mouve- 
ments ; ce que je verifiai bientot par cette autre expe- 
rience. 

(50.) Experience R. Ayant coupe, a un agneau tout re- 
cemment egorge, la langue pres de sa racine, j'appliquai une 
feuille d’etain a I’endroit de la coupure, et la cuiller d'ar- 
gent a une de ses surfaces ; procedant alors a 4 tablir une com- 
munication, comme il faut, entre ces deux armures m£tal- 
liques, j'eus le plaisir de voir la langue entiere tremousser 
vivement, elever sa pointe, se tourner et se replier de part et 
d’autre, chaque fois et tout le terns qu’une telle communica- 
tion avoit lieu. 

(51.) J’ai repet£ cette experience sur une langue de veau, 
que je posai, armee de la meme maniere de la feuille detain 
pres de sa racine, sur un plat d'argent, pour qu’il fit hoffice 
de Tautre armure ; et le succes fut le meme. Je Tai repetee 
aussi sur la langue d’autres petits animaux, comme souris, pou- 
lets, lapins, &c. et j'obtins presque toujours le meme effet. Je 
dis presque toujours, car quelques fois il manqua dans la langue 
des petits animaux ; soit que la feuille d'etain ne fut pas ap- 
pliqu^e convenablement a Tendroit juste, ou les nerfs qui 

G 2 


44 Mr. Volta^s Account of Mr. Galvani's Discoveries , &c. 

regissent les mouvements de la langue y ont leur insertion ; 
soit que la langue refroidie eut d£ja perdu sa vitality qui ne 
dure gueres long-tems dans les muscles des animaux a sang 
chaud, comme j'ai deja fait observer, (sect. 2 6.) et particu- 
lierement dans la langue. 

Je suis, &c. 

A. VOLTA. 


Octobre 25, 1792. 


r 45 : 


W. Further Particulars respecting the Observatory at Benares, 
of which an Account, with Plates, is given by Sir Robert 
Barker, in the LXFIIth Vol. of the Philosophical Transactions. 
In a Letter to William Marsden, Esq. F. R. S. from John 
Xloyd Williams, Esq. of Benares. 

Read January 31, 1793. 


DEAR SIR, 

In conformity with your request, I have now the pleasure of 
sending you an account of the measurement of the different; 
parts of the Benares observatory, called maun-mundel, as taken 
by myself, with a two-foot rule, and a rod of ten feet very 
exactly divided. An account of the use of the different in- 
struments, though very imperfect, was given me on the spot, 
by several learned Brahmins who attended me ; one of whom 
is professor of astronomy in the new founded college at Be- 
nares. They all agreed that this observatory never was used, 
nor did they think it capable of being used, for any nice ob- 
servations ; and believe that it was built more for ostenta- 
tion, than the promotion of useful knowledge. 

In my inquiry into the particulars of the building, I have 
been assisted by my friend the Nabob Ali Ibrahim Kaun, 
.and I believe this account may be relied on. 


46 Mr. Williams's further Particulars 

A.* The large quadrant, called in Arabic, kootoop-bede ; in 
Hindoo, droop, the name of the north polar star. This in- 
strument is built of stone, fixed in mortar, and clamped with 
iron in a very clumsy manner ; between most of the stones 
are spaces of part of an inch. The stile, in its length 
from north to south, measured 39 feet 6\ inches ; the height 
of the south end, 5 feet 4^ inches ; height of the north end, 
22 feet 3 inches. This stile consists of two walls 1 1\ inches 
thick, with a flight of 27 steps between ; and on the outer edge 
of each of these walls are fixed two iron rings. The distance 
between the two rings is 5 feet 8| inches ; from the upper- 
most to the top, 18 feet 8 inches ; from the lower one to the 
bottom, 15 feet and \ an inch ; both sides are nearly alike. 
The rings are, each of them, of an inch in thickness, and 
they are let into the wall between two stones ; the holes 
through which the object is to be viewed are -y^ths of an 
inch in diameter, fths of which space, in each, is covered 
by the projection of the stone. The radius of one of the 
quadrants, on which the hour lines are marked, from the 
outer part of the wall of the stile to the inner edge of 
the arc, is 9 feet and ^ths of an inch ; that of the other, 
9 feet one inch. The width of the rim of the quadrants, 
which are inclined to a line perpendicular to the shadow 
falling from the gnomon, is 5 feet 10^ inches. The qua- 
drant is divided into 6 gurries, and each gurry into 10 

On the outer wall of the stile, fronting the east, at the 



* The references are to the plates annexed to Sir Robert Barker’s account. 


47 


respecting the Observatory at Benares. 

height of 10 feet and 10 inches from the base, are fixed two 
iron pins, each forming a centre, from which circular lines 
are drawn, intersecting each other, as in the annexed repre- 
sentation ; 



with a parallel line drawn underneath, which has the hour, 
or gurry and pull lines marked on it. The wall is plastered ; 
and there are, on other edifices fronting the east, similar lines 
drawn ; the use of which, I understood, was to ascertain the 
time of the day. 

B. An equinoctial dial, called gentu-raje . — It is a circular 
stone, fronting north and south, but inclining towards the 
south. The diameter of the south face is 2 feet inches, a per- 
pendicular line falling from the top will give one foot distance 
from the bottom of the inclined plane. In the south front of 
this stands a small stone pillar, distance 3 feet 8 inches ; a 
line drawn from the centre of this dial to the point on the top 
of the pillar, will, by its shadow, give the time of the day. 
On the nadir side of this dial, the stone is 4 feet 7 inches 
diameter ; on the centre of which is a small iron stile, with 
a hole in it, perpendicular to its plane ; and in the perpendi- 
cular line of the chord are placed two small irons. A line 
passing through the hole in the stile, and each end applied 
to the forementioned irons, gives a shadow, which denotes the 
hour, &c. 

C. A brass circle in the line of the equator, facing north 


48 Mr. Williams’s Particulars 

and south. It has a moveable index, turning on a pivot 
in the centre ; the circle is divided into 360 degrees, or wise, 
subdivided again into 60', and again into 6", and into ^ths. 
This instrument is called cund-brit , or cranti-brit, but I could 
not learn the use of it. 

D. A double circular wall, with a round pillar in the 
centre, as described by Sir Robert Barker. The floor be- 
ing broken, and uneven, renders the height of the outer wall 
irregular, but it measured from 8 feet 1 inch, to 8 feet 3 
inches ; diameter inside, 27 feet 6 \ inches ; thickness of the 
wall, 2 feet. The inner wall is 18 feet within; thickness of 
this wall, 1 foot 5^ inches. The diameter of the centre pil- 
lar, 3 feet inches. 

At the four cardinal points, on the top of the outer wall, 
are four iron pins, with small holes in them, through which, 
the Pundits say, wires are designed to be drawn at the time 
of observation, which wires intersect each other at the centre 
of the pillar. The tops of both the walls are graduated, or 
divided into degrees ; and it is said, that by the shadow of 
these wires falling on the walls, the sun’s declination is 
found. 

In addition to the foregoing, which are described in the 
plates alluded to, on the south-east quarter of the building 
is a large black stone, 6 feet 2 inches diameter, fronting the 
west ; it stands on an inclined plane. I could not learn the 
use of this instrument ; but was informed that it never had 
been completed. There is no other building of any conse- 
quence, nor does it appear there ever was. 

I fear, that from the want of sufficient knowledge of the 
science of astronomy, I have not been able to describe the 


49 


respecting the Observatory at Benares, 

different instruments, and their uses, satisfactorily ; however, 
you may rely on the measurements being taken with the 
greatest exactness. 

For the following description I am indebted to our chief 
magistrate, the Nabob Ali Ibrahim Kaun. 

“ The area, or space comprising the whole of the buildings 
and instruments, is called in Hindoo, maun-mundel\ the cells, 
and all the lower part of the area, were built many years 
ago, of which there remains no chronological account, by the 
Rajah Maunsing, for the repose of holy men, and pilgrims, 
who come to perform their ablutions in the Ganges, on the 
banks of which the building stands. 

“ On the top of this the observatory was built, by the Rajah 
Jeysing, for observing the stars, and other heavenly bodies ; 
it was begun in 1794 Sumbut, and, it is said, was finished in 
two years. The Rajah died in 1800 Sumbut. 

“ The design was drawn by Jaggernaut, and executed un- 
der the direction of Sadashu Mahajin ; but the head work- 
man was Mahon, the son of Mahon a pot-maker of Jeypoor. 
The pundit’s pay was five rupees per day ; the workmen’s two 
rupees, besides presents ; some got lands, or villages, worth 
3 or 400 rupees yearly value ; others money.” 

I am, &c. 

Benares 

March 25, 1792. J. LL. WILLIAMS. 


MDCCXCIII. 


H 


C so 3 


VI. Extracts of two Letters from the Rev. Edward Gregory, 
M. A. Rector of Langar, Nottinghamshire, to the Rev . 
Nevil Maskelyne, D. D. F. R. S . Astronomer Royal ; con- 
taining an Account of the Discovery of a Comet , with Obser- 
vations thereon . 

Read February 7, 1 793, 

.IS ■ , 

Extract of the first Letter , dated Langar, near Nottingham, 

January 10th, 1793. 

J trouble you with this letter to communicate to you such 
observations as I have made of a comet, which I saw on the 
8th instant. The evening of the 8th being very clear, I was 
employed in my observatory, in taking differences of right 
ascension and declination between the planet Venus and 
i Aquarii, when, happening to look towards the north-west 
part of the hemisphere, I saw a star of a hazy appearance, 
and about the size of a star of the second magnitude, in the 
space between the flexure of the Dragon and the foot of Her- 
cules, larger and brighter than I had before remarked in that 
part of the heavens ; which excited my attention so much, as 
to induce me to direct such a telescope to it as lets in much 
light, and is generally used at sea to see objects in the night. 
This star seemed to have a hazy and indistinct appearance in 
the telescope, which immediately led me to suspect it might 
be a comet ; but the twilight yet remaining, I was not quite 


Mr. Gregory's Account of the Discovery of a Comet , &c. 51 

certain of it. When the night was completely come on, it be- 
came evident it was a comet, the coma being of a white light, 
hazy, and ill defined. I could perceive no nucleus, nor as 
yet any appearance of a tail. 

I waited for, and was fortunate enough to obtain, an ob- 
servation of its passage over the meridian under the pole, at 
4 h 8' 30" by Earnshaw's clock, or 4 h 6' 43" sidereal time; 
its zenith-distance, by Bird's quadrant, being 75 0 16' 1 6". 
The observation of the passage over the meridian was taken 
by guessing when a hazy dim appearance, about the shape 
and size of a hen's egg, was in the centre of the field of the 
transit instrument ; any light, however weak, effacing all the 
light of the comet. 

These observations were merely formed from the best judg- 
ment I could make by the naked eye, for, as I before ob- 
served, the light of the comet was so weak, as not to bear 
any degree of light sufficient to render visible the wires 
in the night telescope ; which I have mounted on a polar 
axis, with a proper system of wires to take differences of right 
ascension and declination. 

I continued to watch the comet until three o'clock in the 
morning, when it had ascended to some considerable altitude; 
I could perceive with the night telescope a very faint, but yet 
sufficiently evident tail, and that the comet had moved a few 
minutes to the west ; that is, had increased its right ascen- 
sion, and also its polar distance. I then observed the comet 
with other telescopes, of less aperture and deeper powers ; in 
such it appeared a confused white hazy light, nor could I per- 
ceive any nucleus or tail, although it was visible in the night- 
glass, with its direction towards the zenith. 

H a 


52 Mr. Gregory's Account of the Discovery 

In case you are already apprised of the appearance of this 
comet, and of course this information is superfluous, I hope 
you will attribute my giving you this trouble to my eager 
desire that these extraordinary bodies may be observed with 
such capital instruments as you are in possession of, and also 
to shew you, by these attentions, the sense I entertain of the 
many civilities I have received from you. 

I am, &c. 

EDWARD GREGORY. 

On the 9th I obtained a very imperfect glimpse of the 
comet, the twilight yet being very considerable, and the air 
very hazy. The comet has moved considerably westward, 
and its polar distance, I think, is increased. I thought 
the tail appeared rather brighter and longer ; the coma not 
altered ; no nucleus to be seen. This observation was ex- 
tremely imperfect, the comet being seen with the night-glass 
held in my hand, during a space of four or five minutes ; the 
sky, in that part, was cloudless, though most of the surround- 
ing constellations were obscured. 

Extract of the second Letter, dated January 25th, 1 793. 

The observations of the comet were taken after the fol- 
lowing manner. Finding that any degree of light sufficient 
to render the wires visible effaced the comet, I brought it, as 
nearly as I could judge, into the centre of the field without 
using any light, and then cast light on the illuminator; and in 
that stage of the process between the comet's disappearing 
and the wires becoming visible, I trusted to the impression left 
on the eye for the place of the comet when it vanished ; and 


of a Comet , with Observations thereon . 53 

I think I could not err more than three or four minutes from 
its being on the middle horizontal wire, and about as much 
from the intersection of the vertical, with the middle hori- 
zontal wire. But, after all, it is a vain thing to talk of 
critical exactness in this matter, either in the quadrant or 
transit observations, under the circumstances I am going to 
describe to you. The comet, in the telescopes of these instru- 
ments, had somewhat the appearance of a hen's egg, seen 
obliquely, with the large end towards the eye; of a dull white 
misty light. I could perceive no nucleus, therefore I consi- 
dered the longest diameter, which was nearly directed towards 
the east, (but there was hardly any perceivable difference in 
the diameters) as the line in which, had any nucleus been vi- 
sible, it would have been found ; and I endeavoured, in the 
manner I have described, to bring this line on the middle 
horizontal wire, and the brightest part of it up to the vertical 
wire; and when I thought I had effected this, I read off the 
divisions on the arch, and noted the time by Earnshaw's 
regulator. 

On January 21st, I observed the instantaneous immersion of 
y Tauri, at o h 54/ 22" by my clock; and at 2 h 3' 31" I saw it 
again about a minute's distance from the moon's enlightened 
limb, the moment of emersion having escaped observation. I 
had, on the same day, observed the sun's passage over the me- 
ridian, by a mean of the wires, at 2o h 18' 45^"; the clock had 
been losing a little more than a second a day, for eight or ten 
weeks past.* The mean of ten observations of the first satellite 

* Hence the immersion of the star was at 4 h 34' 48",6, and the first sight of it af- 
ter the emersion at 5 h 43' 46", apparent time. This may perhaps be useful in deter- 
mining the longitude of Mr. Gregory’s observatory. — Note by Dr, Maskelyne, 


54 Mr. Gregory's Account of the Discovery of a Comet, &c . 

of Jupiter place me 3' 47 ", in time, west of Greenwich. My 
latitude, deduced from a great number of observations of the 
sun and stars, in all the various ways of determining the lati- 
tude, with Bird's quadrant, Hadley's quadrant, and two equa- 
torial instruments, is 52 0 54' 37" N. 

It remains that I relate what I saw of the comet's tail. 
At 15 11 astronomical time of the 8th, or three o'clock civil 
time in the morning of the qth, I saw a very faint beam 
of light extending itself from the coma towards the zenith. 
When I brought the coma to the centre of the held of the 
night-glass, which takes in about 7 degrees, it reached to near 
the circumference of the held, consequently it amounted to 
about 3^- degrees. I thought it brighter and longer when I had 
a mere glimpse of the comet in the evening twilight on the 
9th. On the 10th, 11th, and 12th, the tail was rather brighter, 
yet very faint ; not broader than a hnger, nor brighter than 
a beam of light let into an ill darkened room for pris- 
matic experiments. It extended itself beyond the circum- 
ference, when the coma was in the centre of the night-glass, 
perhaps a degree, consequently was 4°^ long; it was inclined 
towards the east, and on the 12th pointed due east at mid- 
night. 

On the 11th, the comet passed the middle wire of the 
transit instrument under the pole, at 8 h 28' o" sidereal time. 
The zenith distance was 56° 2' 15". 

I am, &c. 

EDWARD GREGORY. 


VII. Observations of the Comet of 1793, made by the Rev. Nevil Maskelyne, 
D. D. F. R. S. Astronomer Royal, and other Observers. Communicated by the 
Astronomer Royal. 


Read February 14, 1793. 


1793. 

Mean Time 
at 

Greenwich. 

A of Comet 
in sidereal 
Time. 

i!£ of Comet in 
Degrees, &c. 

Declination 

of 

Comet. 

Longitude 

of 

Comet. 

Latitude 

of 

Comet. 

Name of Observers. 

Jan r /. 

H. M. S. 

H. M. S. 

S. 0 ' " 

D. M. S. 

S. D. M. S. 

D. M. S. 


8 

1 1 

H 

18 

8 55 7 

13 3 5 ° 

11 38 0 

9 26 6 

16 6 43 

20 27 56 
1 12 48 
1 53 28,6 

8 1 40 45 

10 6 59 0 

0 18 12 0 

0 29 37 9 

5 1 46 23 N 
71 1 42 N 

45 53 i 2 N 
17 47 7 N 

7 2 2 9 3 
1 5 16 0 

1 6 16 29 
1 3 45 36 

69 38 5 N1 

76 9 8Nj 

34 53 33 N 
5 >9 33 


Mr. Gregory. 
Mr. STEPH. Lee. 

z 1 

8 5 52 

2 1 1 42,8 

1 2 55 42 

9 1 26 N 

1 3 47 57 

4 0 25 S 



26 

6 54 35 

2 22 42 23 

1 5 4 ° 33 

1 48 19 N 

1 3 5 8 5 ‘ 

ii 43 25 S 



27 

7 37 41 

2 24 4 19 

1613 

051 36 N 

1 3 59 3 ° 

12 43 44 S 



28 

6 5 6 35 

2 25 18,35 

1 6 19 35 

0 4 1 1 N 

14 1 22 

13 3 + 3 6 s 


The Astronomer 

3 ° 

8 57 38 

2 27 41,4 

1 6 55 21 

1 20 59 S 

1 4 7 13 

15 6 48 S 


Royal. 

Feb. 









3 

7 1 * 5 Z 

2 31 27.2 

1 7 5 1 48 

3 17 27 S 

1 4 22 44 

17 15 20 S 



4 

7412 

2 32 17,2 

1 8 4 18 

3 40 40 S 

1 4 27 4 

17 41 21 S 



5 

7 42 28 

2 33 5>«3 

1 8 16 17 

4 2 42 S 

1 4 3 « J 9 

18 6 6 S 



7 

8 5 26 

2 34 37-55 

— 

1 8 39 23 

4 41 1 1 s 

1 4 40 55 

18 50 1 S- 




These places of the comet may admit of some little change, when the stars 
with which it was compared have been settled by observations with the me- 
ridian instruments. 


C S 6 3 


VIII. Account of the Method of making Ice at Benares. In a 
Letter to William Marsden, Esq. F. R. S. from John Lloyd 
Williams, Esq. of Benares. 

Read February 14, 1793. 

DEAR SIR, 

As the method of making ice in this country, where the 
thermometer, during part of the year, stands at from 95 to 
ioo° in the shade, has something peculiar in it, I trust the fol- 
lowing description of the process will not be unacceptable. 

You know that ice is made in India during the months of 
December, January, and part of February ; but I believe it 
has generally been considered as necessary to the congelation 
of the water, that it should have been boiled. However, I can 
now assure you, as a fact within my own observation for 
these nine years past, that a large quantity of ice has been 
made at this place every year, without any preparation 
whatever ; and I have often seen ice of an inch and 
quarter thick, notwithstanding I do not conceive that the 
atmosphere, at that time, was sufficiently cold to produce the 
effect ; for I have frequently placed a thermometer, with the 
naked bulb on the straw, amidst the freezing vessels during 
the night, and on inspecting it between five and six o'clock 
in the morning (at which time the ice-makers informed me 
the cold was most intense), I never found it below 35 0 . I 


Mr. Williams's Account of making Ice at Benares. 57 

have even seen ice, of a considerable thickness, formed when 
the thermometer was not lower than 40 degrees. 

The method of making ice at Seerore, near Benares, is as 
follows. 

A space of ground of about four acres, nearly level, is divided 
into square plats, from four to five feet wide. The borders 
are raised, by earth taken from the. surface of the plats, to 
about four inches ; the cavities are filled up with dry straw, 
or sugar-cane haum, laid smooth, on which are placed* as 
many broad shallow pans, of unglazed earth, as the spaces 
will hold. These pans are so extremely porous, that their 
outsides become moist the instant water is put into them ; 
they are smeared with butter on the inside, to prevent the 
ice from adhering to them, and this it is necessary to repeat 
every three or four days ; it would otherwise be impossible to 
remove the ice without either breaking the vessel, or spending 
more time in effecting it than could be afforded, where so much 
is to be done in so short a time. In the afternoon these pans 
are all filled with water, by persons who walk along the borders 
of ridges. About five in the morning, they begin to remove 
the ice from the pans ; which is done by striking an .iron hook 
into the centre of it, and by that means breaking it into se- 
veral pieces. If the pans have been many days without 
f smearing, and it happens that the whole of the water is 
frozen, it is almost impossible to extract the ice without 
breaking the pan. The number of pans exposed at one time, 
is computed at about 100,000, and there are employed, in fill- 
ing them with water in the evenings, and taking out the ice 
in the mornings, about 300, men, women, and children ; the 

l 


MDCCXCIII. 


58 Mr. Williams's Account of making Ice at Benares. 

water is taken from a well contiguous to the spot. New 
vessels, being most porous, answer best. 

It is necessary that the straw be dry ; when it becomes wet, 
as it frequently does by accident, it is removed, and replaced. 
I have observed water which had been boiled, freeze in a 
china plate ; yet having frequently placed a china plate, with 
well-water, among the unglazed pans on the straw beds, I 
found that when the latter had a considerable thickness of ice 
on them, the china plate had none. I have also wetted the 
straw of some of the plats, and always found it prevented the 
formation of ice. The air is generally very still when much 
ice is formed ; a gentle air usually prevails from the south- 
westward about daylight. I had a thermometer among the 
ice pans, during the season of making ice, with its bulb placed 
on the straw, and another hung on a pole gj feet above 
the ground ; and commonly observed, that when ice was 
formed, and the thermometer on the straw was from 37 to 
42 0 , that on the pole would stand about 4 degrees higher ; 
but if there was any wind, so as to prevent freezing, both the. 
thermometers would agree. 

I shall offer no opinion respecting the causes of ice being 
formed when the thermometer is so many degrees above the 
freezing point 5 but hope the subject will be elucidated by 
some more capable person. 

I am, &c. 

Benares, 

March 25, 1792, J» LL. WILLIA1VIS, 


L 59 3 


IX. Account of tzvo Instances of uncommon Formation , in the 
Viscera of the Human Body. By Mr. John Abernethy, As- 
sistant Surgeon to St. Bartholomew's Hospital. Communi- 
cated by Sir Joseph Banks, Bart. P. R. S. 


Read February 14, 1793. 

I take the liberty of presenting to the Royal Society, the 
relation of two cases of uncommon formation of the human 
body. When animal existence is supported by any other 
than the usual admirably contrived means, it cannot fail to 
excite the attention of the philosopher, since it shews to him 
the powers and resources of nature. 

The peculiarities of the first case which I have the honour 
to offer to the Society, consist in an uncommon transposition 
of the heart, and distribution of the blood vessels ; together 
with a very strange, and, I believe, singular formation of the 
liver. The body which contained these deviations from the 
usual structure was brought to me for dissection ; with its his- 
tory whilst alive, I am therefore unacquainted. The subject 
was a female infant, which measured two feet in length ; the 
umbilicus was firmly cicatrized, and the umbilical vein closed ; 
from these circumstances I conclude that it was about ten 
months old. The muscles of the child were large and firm, 
and covered by a considerable quantity of healthy fat ; in- 
deed the appearance of the body strongly implied that the 
child had, when living, possessed much vigour of constitution. 

I 2 


So Mr. Abernethy's Account of two Instances of 

I shall first relate those varieties of the sanguiferous system 
which were found on the thoracic side of the diaphragm, and 
afterwards describe those which were discovered in the abdo- 
men ; this will naturally lead me to the account of the un- 
common state of the liver. The situation of the heart was re- 
versed ; the basis of that organ was placed a little to the left 
of the sternum, whilst its apex extended considerably to the 
right, and pointed against the space between the sixth and 
seventh ribs. The cavities usually called the right auricle 
and ventricle were consequently inclined to the left side of 
the body ; therefore, to avoid confusion in the description, I 
shall, after Mr. Winslow, term them anterior, whilst those 
cavities usually called left, I shall term posterior. The in- 
ferior vena cava past, as usual, through a tendinous ring in 
the right side of the centre of the diaphragm, it afterwards 
pursued the course of the vena azygos, the place of which it 
supplied ; after having united with the superior cava, the 
conjoined veins passed beneath the basis of the heart, to ex- 
pand into the anterior auricle. The veins returning the 
blood from the liver united into one trunk, which passed 
through a tendinous aperture in the left of the centre of the 
diaphragm, and terminated immediately also in the anterior 
auricle. 

The distribution of blood to the lungs, and the return 
of it from those bodies, were accomplished after the usual 
manner. 

The aorta, after it had emerged from the posterior ven- 
tricle of the heart, extended its arch from the left to the right 
side, but afterwards pursued its ordinary course along the bo- 
dies of the dorsal vertebrae. 


uncommon Formation in the Viscera of the Human Body, 6 . 1 

From the curvature of the aorta there first arose the com- 
mon arterial trunk, which, in this subject, divided into the left 
carotid and subclavian arteries ; whilst the right carotid, and 
subclavian, proceeded from the aorta by distinct trunks. 

The inferior aorta gave off the czeliac, which, as usual, di- 
vided into three branches ; however, that artery which was 
distributed to the liver appeared larger than common ; it 
exceeded, by more than one-third, the size of the splenic 
artery of this subject. This was the only vessel which sup- 
plied the liver with blood, for the purpose either of nutrition, 
or secretion. 

The vena portarum was formed in the usual manner, but 
terminated in the inferior cava, nearly on a line with the 
renal veins. The umbilical vein of this subject ended in the 
hepatic vein. 

The liver was of the ordinary size, but had not the usual 
inclination to the right side of the body ; it was situated in the 
middle of the upper part of the abdomen, and nearly an equal 
portion of the gland extended into either hypochondrium. 

The gall bladder lay collapsed in its usual situation ; it was 
of a natural structure, but rather smaller than common ; it 
measured one inch and a half in length, and half an inch in 
breadth. On opening the bladder, we found in it about half 
a tea-spoon full of bile ; in colour it resembled the bile of 
children, being of a deep yellow brown ; it also tasted like 
bile ; it was bitter, but net so acridly or nauseously bitter 
as common bile. 

I diluted a small quantity of this fluid with water, and 
with this liquor moistened some paper which had been 
tinged with a vegetable blue; this was instantly changed. 


6a Mr . Abernethy's Account of two Instances of 

into a deep green, consequently this fluid, like common bile, 
abounded with alkali. I added some diluted nitrous acid to a 
small quantity of this, and of common bile ; they both be- 
came changed, by this addition, to a similar green colour. 
The colouring matter of the bile therefore appears to have 
possessed its common properties. 

The gall ducts had been divided, in removing the stomach 
and duodenum, before the uncommon termination of the vena 
portarum was discovered, and some bile had flowed from the 
divided ducts. 

The intestines did not contain much alimentary or fcecal 
matter ; this was, however, as usual, deeply tinged with bile. 

The spleen consisted of seven separate portions, to each of 
which a branch of the splenic artery was distributed. The 
other viscera were sound, and of their usual structure and ap- 
pearance. 

No cause could be discovered to which the child’s death 
could be assigned. We observed that the tongue was in- 
crusted with a dark coloured mucus, which indicated the 
existence of fever previous to the infant’s death. 

When an anatomist contemplates the performance of bi- 
liary secretion by a vein, a circumstance so contrary to the 
general economy of the body, he naturally concludes, that 
bile cannot be prepared unless from venal blood ; and he also 
infers, that the equal and undisturbed current of blood in the 
veins is favourable to the secretion ; but the circumstances of 
the present case, in which bile was secreted by an artery, 
prove the fallacy of this reasoning. I extremely regret that 
only so small a quantity of this bile could be collected from 
the gall bladder ; as, surely, it was very desirable to ascertain 


uncommon Formation in the Viscera of the Human Body. 63 

more fully how far the qualities of this curiously prepared 
fluid resembled common bile. 

That the fluid secreted by the liver was not, in this case, 
deficient in quantity, appears to me sufficiently evident. If 
the gait bladder had not suffered occasional repletion, I think 
it would have been found in a state of greater contraction. 
Some bile had escaped from the divided gall ducts, and a con- 
siderable quantity of .his fluid would be required to give so 
deep a tint, as in this case was visible, to the alimentary 
matter. 

I cannot, therefore, but suppose that the empty state of 
the gall bladder was the effect of accident, and not of defi- 
cient secretion by the liver. The bulk and well nourished 
state of the body do, I think, demonstrate that there was no 
defect in the functions of the chylopoetic organs. 

But it will surely be inquired, from what cause the death of 
the child originated. It may be suspected that the mal-forma- 
tion of the liver contributed to its decease ; and particularly 
as no derangement of any vital organ could be discovered. 
Yet if it be considered how frequently children die from 
nervous irritation, or fever, the probability of this suspicion is, 
in my opinion, diminished. The circumstances of the case 
may impress others with contrary sentiments ; I shall re- 
main satisfied with having faithfully described the appear- 
ances of the body, and having offered those remarks which I 
believed deducible from them. 

The peculiarity of the next case, which I have the honour 
to lay before the Society, consists in an uncommon formation 
of the alimentary canal. The body of a boy was brought to 
me for dissection ; it measured four feet three inches in 


t >4, Mr. Abernethy's Account of two Instances of 

length ; it was well formed, and had moderately large limbs ; 
they, however, appeared flabby, as if wasted by recent 
disease. 

The abdomen was enormously swoln ; which being opened, 
there appeared a more than ordinary extent of large intes- 
tines, in a state of great distention. 

The diameter of the canal measured about three inches, 
and its dimensions were nearly equal in every part. 

The matter with which it was turgid was of a greyish co- 
lour, of a pulpy consistence, having little foetor, and quite 
unlike the usual foecal contents of the large intestines. 

The length of the colon was uncommon ; having, as usual, 
ascended to the right hypochondrium, it was reflected down- 
wards, even into the pelvis; it then reascended to the left 
hypochondrium, and afterwards pursued its usual course. 

After turning aside this large volume of intestine, to exa- 
mine the other parts of the alimentary tube, we were sur- 
prised to discover that the subject contained scarcely any 
small intestines. These viscera, with the stomach, lay in a 
perfectly collapsed state; their texture was extremely tender; 
they were torn even by a gentle examination. The duode- 
num, jejunum, and ileum, when detached from the body, and 
extended, measured only two feet in length, whilst the ex- 
tent of the large intestines exceeded four feet. 

The utmost length of the intestinal tube, in this subject, 
was little more than six feet, whereas it should have been 
about twenty-seven feet, had it born the ordinary propor- 
tion to the length of the body. 

I distended and dried this curious alimentary canal, and 
still have it in preservation. 

As the small intestines measured only two feet in length. 


uncommon Formation in the Viscera of the Human Body. 65 

this extent was doubtless insufficient for the preparation and 
absorption of chyle ; these processes must therefore have 
been, in a great degree; performed by th^large intestines. 

The form and stature of the boy shew that nutrition was 
not scantily supplied ; he died evidently from a want of in- 
testinal evacuation. Whether the unusual structure of the 
canal contributed to the production of disease, cannot, per- 
haps, be readily determined ; it appears, however, very pro- 
bable that uncommonly formed parts, although capable of 
supporting life, may be less adapted to sustain the derange- 
ment of functions consequent to disease. 

In Tab. VII. and VIII. are represented the appearances 
described in the first of the foregoing cases. 

Tab. VII. 

A. The anterior ventricle, which is usually inclined to the 
right side. 

B. The anterior auricle. 

C. The posterior ventricle, which is usually inclined to 
the left side. 

D. The posterior auricle. 

E. The superior vena cava. 

F. The aorta. 

G. The pulmonary artery. 

H. The common trunk of the left carotid, and subclavian 
arteries. 

I. The right carotid. 

K. The right subclavian. 

L. The hepatic vein. 

M. Part of the diaphragm. 

MDCCXCIII, K- 


66 Mr. Abernethy's Account of two Instances , 

N. The liver. 

O. The superior mesenteric artery. 

P. The renal artery. 

Q. The renal vein. 

R. The vena cava inferior. 

S. The aorta continued. 

T. T. The vena portarum. 

Tab. VIII. 

A. The anterior auricle, turned backwards, that the vena 
cava may be seen. 

B. The posterior ventricle. 

C. The posterior auricle. 

D. The superior vena cava. 

E. The inferior vena cava. 

F. The conjoined veins passing beneath the basis of the 
heart to the anterior auricle. 

G. The beginning of the vessels of the right lung. 

H. The pulmonary artery. 

I. The aorta. 

K. The hepatic vein. 

L. Part of the diaphragm. 

M. The liver. 

N. The cseliac artery. 

O. The hepatic artery. 

P. The splenic artery. 

Q. The renal artery. 

R. The superior mesenteric artery. 

S. The renal vein. 

T. T. The vena portarum. 


Philos. Trans. MDCCXCIII Tab.VO.. p .66. 







/ 



C 67 3 


X. Account of the Equatorial Instrument. By Sir George 
Shuckburgh, Bart. F. R. S. 


Read March 21, 1793. 

“ Juvat ire per altum 

“ Aera, et immenso spatiantem vivere ccelo ; 

“ Hoc sub pace vacat tantum.” Manilius, lib. i. 

(1.) Before I enter upon the description of the instrument 
which I propose particularly to describe, it may not be im- 
proper to say something of the equatorial in general, and of 
such instruments as, having been made upon a similar prin- 
ciple, have been used by different astronomers, in different 
ages. 

The first account, that I meet with, of an astronomical in- 
strument that bears any resemblance to it, is to be found in 
Ptolemy, (lib. 5 of his Almagest) wherewith, he tells us, 
he determined the distance between the two tropics. This 
instrument is described under the name atrrpoXo'MiKOv opyuvov, 
and appears to have consisted of two circles, placed at right 
angles to each other, one representing the meridian or sol- 
sticial colure, and the other the zodiac ; the former turning 
upon an axis, placed parallel to the axis of the earth, being 
elevated to the latitude of the place, and the other turning 
within it on two centres, removed 23-t 0 from the former axis ; 
and was in truth not very unlike the common ring dial, only 

K 2 


68 Sir George Shuckburgh’s Account 

about six times as large. Each circle was divided into 360*, 
and those again into three or four subdivisions, and being 
furnished (it may be supposed) with moveable sights, the 
observer was enabled to take the elevation or depression of 
any object above or be'ow the ecliptic, together with its dis- 
tance from the meridian, or colure, that circle being previ- 
ously placed parallel to its corresponding one in the heavens. 
The first measure would give the latitude of any heavenly 
body, and the latter the longitude. This instrument, or 
something similar to it, seems to have been in use as early as 
the time of Hipparchus, who lived in the second century 
before our Saviour, (vide Weidleri Hist. Astron. p. 319; et 
Tychonis Brahe Mechanic a ) and was continued to be used 
by astronomers for upwards of fifteen centuries afterwards. 

(2.) The next account that occurs is by J. Muller, Re- 
giomontanus, sive Joannes de Monte Regio, who flou- 
rished about A. D. 1460, and, in a posthumous treatise ex- 
pressly on this subject, intitled Scripta clarissimi Matbema - 
tici M. Joannis Regiomontani de Torqueto, Astrolabio 
armillari , Reguld magnd Ptolemaica, Baculoque Astronomico, 
&c. &c. in quarto, printed at Nuremberg in 1544, has 
given a pretty full account, not only of the armillary as- 
trolabe, but also of the torquetum, which in fact was no- 
thing more than a portable equatorial, and may be consi- 
dered as the first instrument truly of this kind. As this trea- 
tise is become extremely scarce, and I know of only one 
copy in this kingdom, I take this opportunity of apprizing 
the curious, that it is to be met with in the British Museum. 
A short description, however, of the torquetum, with a pi ate 
©f the instrument, will be found in Mons. Bailly's Astro - 


of the Equatorial Instrument. 6g 

nomie fyfoderne, Tome I. p. 6 87 ; and a description of the as- 
trolabium armillare of Ptolemy, according to Regiomonta- 
nus's conception of it, who may be considered as the best com- 
mentator upon the Almagest now to be met with, will be 
found in Weidler’s Historia Astronotnix, quarto, 1741. 

(3.) The next autnor that presents himself is Copernicus, 
(who lived in 1530) and in his work De Revohitione Orbium 
ccelestium , lib. 2. c. 14. De exquirendis Stellar um Locis, pro- 
fessedly describes the same instrument with Ptolemy ; but, 
as it appears to me, something more complicated, having a 
greater number of circles, and in truth what in later times has 
been understood by the name, Armillary Sphere. 

(4.) After Copernicus, 1 find, in a work of Apian, who 
was his contemporary, or a little after him, viz. about 1538, a 
complete description of the torquetum , with all the parts of 
it minutely detailed, assisted by four or five wooden plates, 
together with the use of the instrument. This work, which 
is also very scarce, is in folio, intitled, Introductio geographica 
Petri Apiani in djctissimas Verneri Annotationes , &c. &c. cui 
recens jam opera P. Apiani accessit Torquetum , Instrumentum 
pulcherrimum sane et utilissimum . Ingolstadii , anno 1533. To- 
wards the conclusion of this work is a curious letter of Re- 
giomontanus to Cardinal Bessarion, De Compositione Me- 
teoroscopii, that is, the armillary sphere that was used by 
Ptolemy, with a plate of it. 

(5.) To Apian succeeded, at some distance, but exceeded all 
that went before him, the justly celebrated Tycho Brahe, 
who in his Astronomies Instauratce Me, hanica* Noribergce , 1602, 

* See also Hist . Coelestis , Lib . Prolegom . Tychonis Brahei, Augustes Viudeli - 
corum, 1666, II. Vol. folio, p. 118 and 119. 


7© Sir George Shuckburgh's Account 

folio, has given us a description and wooden plates, of no less 
than four different astrolabes, under the names of armillce 
zodiacales et equatoricc , of different sizes, from 4-f to 10 feet 
diameter, divided into degrees and minutes, and some of 
them into every 15 or 10 seconds, but furnished only with 
plane sights. These large instruments were placed in towers 
appropriated to each, with moveable roofs, one half of which 
was taken away at the time of observation. A circumstance 
that it is curious to remark, is, that Tycho, who was atten- 
tive to every thing that could improve the accuracy of his ob- 
servations, made the axis of his 10 feet circle hollow, “ Axis 
“ ejus e chalybe constans, et undiquaque apprime teres ; in- 
“ terius tamen cavus, lie pondere officiat, in diametro est 
“ trium digitorum a principle that has been very prudently 
re-adopted in these later times, as will be presently seen. 

(6.) After Tycho 1 meet with no instrument of this sort 
till the time of Christopher Scheiner, about the year 1620, 
who made use of a small telescope, moving upon a polar axis, 
with an arc of 47 0 of declination, to observe the sun's disc 
commodiously, and examine his spots ; an account of which 
will be found in his Rosa JJrsina, folio, Bracciani, 1630, p. 
347. But this instrument can hardly be considered as an 
astronomical one, being merely a contrivance to follow the 
sun with a telescope, by means of one motion only, similar in 
its object with the heliostate, described by Dr. Desaguliers, 
(Mathematical Elements of Natural Philosophy, lib. 5. c. 2.) 

(7.) Again, Flamsteed's sector, which he has described 
in the prolegomena to the third volume of his Historia Cce~ 
lestis , p. 103, though mounted upon a polar axis, and very in- 
geniously contrived for the purpose it was intended for, viz. 


of the Equatorial Instrument . 71 

to measure the angular distances between the stars, having 
no divided circle at right angles to the polar axis, to take 
right ascensions, cannot come into the class of equatorial 
instruments. Nor need I here mention Mr. Molyneux's te- 
lescopic dial, ( Sciothericum telescopicum , in 1686 ) though 
depending upon the principle of a polar axis, which, like a 
ring dial, or equinoxial dial, was little more than a play-thing 
for an amateur in astronomy. 

(8.) But about the year 1730 or 1735, when the practice 
of astronomy had assumed a new face in this kingdom, under 
the skill of Dr. Halley and of Dr. Bradley, Mr. Graham 
invented his sector, for taking differences of right ascension 
and declination out of the meridian ; and this may be consi- 
dered as bearing a considerable affinity to the equatorial in- 
strument in principle, and differing from it only in the ex- 
tent of its powers. Of this instrument, which is well known 
to every practised astronomer, a complete account will be 
found in Smith's Optics, Vol. II. § 885. and in Mr. Vince's 
Astronomy. I approach now to the period when the modern 
equatorial instrument, properly so called, took its origin. 

(9.) Mr. James Short, a person of very considerable emi- 
nence for his skill in the theory and practice of optics, and 
particularly for the unexampled excellence to which he had 
carried catoptric telescopes, in which, I believe, he has never 
yet been exceeded : Mr. Short, I say, probably finding him- 
self capable of making telescopes, of very moderate dimen- 
sions, fit for many astronomical purposes, and able to exhibit 
several of the heavenly bodies by daylight, provided they 
were furnished with a convenient apparatus and movement 
for that purpose, applied a two feet reflecting telescope, for 


7$ Sir George Shuckburgh's Account 

the first time, to a combination of circles, representing the 
horizon, the meridian, the equator, and moveable horary 
circle, or circle of declination, each divided into degrees, and 
every third minute, furnished with levels, &c. for adjustment 
to the place of observation. This machine was invented in or 
before the year 1749, and is described in the Philosophical 
Transactions for that year. But as this instrument was fur- 
nished with no counterpoises in any part, and the length of 
the telescope (two feet) was found considerably too great for 
circles whose diameter was not more than six inches, it became 
unsteady, and unfit for any other purpose than that of finding 
and following a celestial object, and, on account of its high 
price also, was, as far as I believe, but little made use cf. 

(10.) However, after some years had elapsed, the idea of 
an equatorial telescope was again renewed by three several 
artists in this kingdom, Messrs. Ramsden, Nairne, and Dol- 
lond, with many and very material improvements, such as 
to carry the portable equatorial almost to perfection. Of this 
instrument Mr. Ramsden had made three or four, as early, 
I believe, as the year 1770 or 1773; viz. one for the late 
Earl of Bute, one for Mr. M‘Kenzie, another for Sir Jo- 
seph Banks, and lastly, one for myself ; with which I made 
a great many astronomical and geometrical observations in 
France and Italy, in the years 1774 and 1775, some of 
which may be seen in a Memoir upon the Heights of 
some of the Alps, printed in the Philosophical Transac- 
tions for 1777. Of this machine a plate and description in 
French was printed in the year 1773, an d reprinted in 
English in 1779. An ample account of this equatorial will be 
found in Mr. Vince's Treatise on practical Astronomy, p. 152. 


of the Equatorial Instrument. 75 

In 1771 Mr. Nairne published an account of his equatorial 
telescope, in the Philosophical Transactions for that year; and 
in 1772 or 1773 Messrs. P. and J. Dollond printed an account 
of theirs. Each of these instruments were furnished with coun- 
terpoises, and, in general principles, were at least similar, if 
not the same. The preference that I was inclined to give at 
that time to my own instrument, made by Mr. Rams den, 
was owing to the peculiar advantage of a swinging level, to 
the unexampled accuracy of its divisions, and its great porta- 
bility. If, in what I have just now said of the three last in- 
struments, I should have committed any error with respect to 
the priority of their improvements, I must leave that point 
to be settled by the artists themselves, and shall hasten to the 
description of the instrument I set out with. But first one 
word with respect to an instrument that has been in frequent 
use on the continent, called, very absurdly, a Parallactic Ma- 
chine. 

(11.) The first notice, that I find of it, is in the History of 
the Academy of Sciences at Paris, for 1721, p. 18, in a me- 
moir of Mr. Cassini, with a description and plate of it ; also 
in the History of the same Academy for 174b, p. 121, wherein 
it is said to have been proposed by Mr. Passement, but 
without any description of it ; it will, however, be found 
described, with a plate of it, in the Dictionnaire de Mathema - 
tique, par Mr. Saverien, two vols. quarto, 1753 ; and this ac- 
count has been copied into Owen's Dictionary of Arts and 
Sciences, in four vols. octavo. It appears to have been a 
frame of wood supporting a polar axis, with an equatorial 
and declination circle, of only a few inches in diameter ; and 
was in fact no more than a very bad stand to a refracting, 

L 


MDCCXCIII. 


74 


Sir George Shuckburgh's Account 


telescope of 8 or 10 feet long, giving it a motion parallel to 
the equator ; and hence some person, not very learned, gave it 
the name. Machine parallactique, as if 7rapaXXayC\<& and rrapaX- 
Xi]X<&> were the same word. It is true that the early astrono- 
mers did use a machine called Regulce parallactic ce, but that 
was an instrument to take the altitudes of the moon, and 
from thence to determine her parallax. Nor can I say much 
in favour of a machine of the same name, described in Mr. 
La Lande’s Astron. Vol. II. § 2004, which certainly does 
not do a great deal of credit to the state of the mathematical 
arts amongst the French; it however may have its conve- 
nience, as it is probably attainable at a very small expence. 
The author last mentioned speaks (§ 2409) of an equatorial 
in his possession, made by one Vayringe in 1737, with 
circles of 7 or 8 inches diameter, but of what construction we 
are not informed ; and the name of the artist is, I confess, 
totally new to me. An instrument also of this nature, made 
by Megnie, for the President De Saron, is described, and 
seems to be well imagined for a portable machine. This 
very amiable and ingenious gentleman, Mons. De Saron, 
was so obliging, amongst other civilities when I was at Paris 
in 1775, to shew me a small reflector upon an equatorial 
stand, with some wheel work to keep it constantly following 
a star, together with an apparatus for the refraction, altitude, 
and azimuth, if I recollect right ; and in the year 1778 Mr. 
William Russel, a late worthy member of the Royal So- 
ciety, shewed me a small instrument of the same kind, that 
had been made by the late Mr. Bird. 

( 12.) From the preceding account, it must appear that the 
equatorial instruments hitherto made, either from the small- 


of the Equatorial Instrument . 75 

ness of their dimensions, or defect of their constructions, were 
totally unfit for the accuracy of modern astronomy, where an 
error of a few seconds only, in an observation, is all that can 
be admitted, to entitle it to any credit.* With respect to the 
precision of astronomical instruments in general, I may no- 
tice by the way, that from the time of Hipparchus and 
Ptolemy, before and at the commencement of the Christian 
sera, to the age of Walther and Copernicus, in the begin- 
ning of the 16th century, few observations can be depended 
on to within less than 5, 8, or perhaps even 10 minutes; 
those of Tycho Brahe, indeed, that princely promoter of as- 
tronomy, to within one minute. The errors of Hevelius's 
large sextant of 6 feet radius, towards the middle of the last 
century, might amount to 15 or 20 seconds. Flamsteed's sex- 
tant to 10 or 12 seconds ; and lastly, those of Mr. Graham's 
mural quadrant of 8 feet radius, with which Dr. Bradley 
made so many observations from 1742, might amount to 
7 or 8 seconds. 

( 13.) Having said thus much generally upon the subject of 
this ingenious instrument, and not more, I trust, than will be 
deemed, by every lover of this science, what its importance de- 
serves, I proceed to the description of one I have caused to be 
made by a very able artist of this metropolis, Mr. Jesse Ramsden. 

AB, CD, EF, GH, (Tab. IX.) are 4 columns composed 
of hollow brass tubes g\ inches in diameter, and 5 feet 10 
inches long ; these, with two others, one of which appears 


* I must except from this remark the two large equatorial sectors made by Mr. 
Sisson, for Greenwich observatory; and also an instrument of this kind, made by Mr. 
Ramsden, for the late General Roy, and now in the possession of Mr, Aubert, 
whose circles are about 30 inches in diameter. 

L 2 


76 Sir George Shuckburgh's Account 

in part at IK, and the other wholly hid behind EF, are 
firmly fixed, at their upper ends, to a circle of bell metal, 
B D F H, and, at their lower end, to an inverted truncated 
hollow cone* LLL, of brass, in height 2 feet, and in diameter 
at its base AG, 1 foot 9 inches. The cross pieces or tubes 
P, P, as likewise 0 , 0 , and 0 , 0 , serve to connect the co- 
lumns more strongly together, and prevent their bending. 
These several parts constitute the principal axis of the instru- 
ment, the lower end of which terminates in a steel point or 
cone, resting in a hollow conoid of bell metal, in such man- 
ner that the apex of the former does not reach to the bottom 
of the latter, but the place of bearing, and of friction, is (it 
may be) about two-tenths of an inch from the extremity of 
the cone ; the other end of this axis finishes in a cylindrical 
pivot N, of about 1^ inch long, and 1 inch in diameter, turn- 
ing in a Y of bell metal. The entire length of this axis is 
8 feet 4 inches, the lower end being supported by an iron 
frame 3, 4, 5, 6, 7, 8, which is firmly fixed, below the floor, 
into brick work, and, by means of two iron bars, one of which 
is seen at 28, and the other on the opposite side, not visible 
in the drawing, is kept secure from any motion eastward or 
westward ; the lower part of this frame, to about one foot 
high, is inclosed by a mahogany box, or case, 9, 10, the top 
of which is intirely covered up, and serves as a die or base to 
this end of the instrument. The other extremity of this long 

* Upon this cone are inscribed the following words . — “ Hocce Panorganon Ura- 
“ nometricum a Jesse Ramsden, Londinensi Optico celeberrimo, et omnibus id 
“ genus artificum longe anteponendo, excogitatum, decern post annos nunc tandem 
“ absolutum, Georgius Shuckbursh Baronettus, in testimonium amoris sui erga 
“ res astronomicas, et ad easdem promovendas, fieri curavit, anno 1791.” 


77 


of the Equatorial Instrument. 

axis, viz. the pivot N, rests upon the strong iron support 29, 30, 
31, standing ten feet above the floor, made of massive pieces 
of cast iron, 2^ inches wide, and \ inch thick, and held firmly 
together by bolts and nuts, as in the figure. 32, and 33, are two 
iron bars nearly at right angles to each other, and at \ right 
angles to the meridian, that connect this upright support 
with the walls of the building, and, going through the bricks, 
are held fast by iron collars and nuts on the outside of the 
wall ; these bars or braces resist any tendency, from the 
weight or pressure of the instrument, to push the supporter 
29, 30, and 31, out of its upright position; and, being at right 
angles to each other, serve to keep it steady with respect to 
any lateral force that may accidentally be applied. The lower 
part is continued below the floor, and firmly fixed, with mor- 
tar and lead, into the brick work of the arch which will be 
presently described. The bottom is shut up in a box or 
plinth of mahogany, 34, 35, as has been mentioned in the 
description of the frame supporting the other end of the axis, 
at 9, 10. Near the lower end of the principal axis LN, are 
inserted 10 concentric brass cones or radii, a a, hh, cc, dd, ee, 
carrying on their extremities a graduated brass circle, of 4 feet 
diameter,* at right angles to the principal axis already de- 
scribed ; this circle has two sets of divisions, one of points, and 
one of lines, each into degrees, and every 10 minutes, and the 
intermediate minutes and seconds are read off by the micro- 
scopes W and X, with a moveable wire and micrometer 
screw, such as has been described in General Roy's Account of 
his Instrument for measuring horizontal Angles. (See Philo- 
sophical Transactions, Vol. LXXX. p. 145.). The circle just 

* More correctly 49J inches. 


78 Sir George Shuckburgh's Account 

mentioned is inclosed by a circular frame, or rail of mahogany, 
14, 15, which is supported by ten balusters, 16, 17, 18, 19, 20, 
si, 22, 23, 24, 25, and serves to protect the brass circle from 
any accidental injury in passing by it, without depriving it of ex- 
posure to the general temperature of the room. It, at the same 
time, affords means of support to a small lamp, 13, which, by 
reflection from the perforated speculum at the bottom of the 
microscopes, to be seen in that marked X, throws light upon 
the divisions by night. 2 6, 26, and 27, are iron rods, that, by 
being attached to the wooden case, 9, 10, give steadiness to the 
upright balusters, and the circular frame that they support. 

1, and 2, are large stout brass cones, firmly fixed into the frame 
3, 4> 5 > 6, 7> 8, before mentioned, and whose use is to carry the 
microscopes W, X ; any degree of pliancy or flexure in these 
cones would be readily discernible in the microscopes, and 
extremely detrimental to the observations, they are therefore 
made as stiff as possible, y, is a plane forming the upper 
side of the frame 3, 4, 5, 6, &c. and consisting of 3 plates, 
two moveable in grooves, and one fixed, furnished with suit- 
able screws, one giving the extremity of the axis a motion 
upward or downward, and the other a motion to the right or 
left : this latter is procured by a rod passing through the cone 

2, one end screwing into the plate below L, near the centre, 
and the other turned by an occasional handle fixed on 
near X ; the former motion, viz. of elevating or depressing 
the axis, is procured by a handle fixed on to a screw near e, 
QR is another circle, of the same dimensions with the former, 
graduated in the same manner, and held together by eight 
conical radii, firmly screwed to a circular centre piece, which 
serves as a base to a large conical axis, 2 feet 3 inches long, 


79 


of the Equatorial Instrument. 

one side of which is seen at U, and its exterior extremity 
near V, with its sliding plate and screws for adjustment. 
Close behind the graduated circle, and at right angles to this 
axis, passing through it, lies the telescope T S, feet long. 
This circle is likewise furnished with two microscopes, and 
micrometers, as in the equatorial circle, one of which is seen 
at full length at Y and Z, the eye tube being at Y, and the 
object glass, with the perforated speculum to throw light, at 
Z ; the other microscope, on the opposite side of the circle, 
is not so discernible in the drawing, being completely fore- 
shortened at Z near T, the eye of the draftsman having been 
exactly in the axis of the tube of the microscope, a, a, a, u, u, 
is an hexagonal lozenge, composed of six brass rulers, firmly 
fixed to the columns AB and EF, and supporting the lower 
end of the microscopes, as the pieces (3/3, (3/3, in like manner, 
sustain the upper end. By these means the wire in the field 
of the microscopes becomes a fixed immoveable index, and, 
after proper adjustment, an exact diameter of the circle, whilst 
the telescope, together with the circle, turns round the coni- 
cal axis before mentioned. At P is a spirit level, passing 
through the centre plate of the conical axis at right angles to 
the telescope, supported by a cock at each end, one of which 
appears at k ; this cock is fixed to the cone U, and, by means 
of a small toothed wheel and pinion, the level is made to re- 
volve round its own axis, so that the same side of the level 
may readily be brought uppermost, whatever position the 
circle be put into ; it is also furnished with all necessary ad- 
justing screws. It will readily be seen that a telescope, thus 
fitted up, will have all the properties of a transit instrument, 


8o 


Sir George Shuckburgh's Account 


while the graduated circle will possess those of a meridian 
quadrant. For this purpose l, m, is a stout brass tube, inclos- 
ing a stiff' iron rod, turning upon two fine steel points, ad- 
justed, by proper screws, parallel to the line of sight of the 
telescope ; this rod is attached to a spirit level of great sen- 
sibility, lying below it, which, with the rod, turns round 
upon the steel points just mentioned, and is in fact a hanging 
level of the best construction. At the eye end of the tele- 
scope S, is a peculiar apparatus to correct the effects of re- 
fraction and parallax, when an observation is made out of the 
meridian : it is composed of two levels, a small quadrant of 
altitude n, o, and a semicircle divided, with its nonius, to 
every 5', on the breech plate of the telescope, the exterior eye 
tube having a circular motion, by a wheel and pinion at 0, in- 
dependent of the tube that carries the cross wires ; by this 
means, the angle of the horary and vertical circles may at 
any time be found, together with the altitude of the object, 
and then, by the resolution of two right angled triangles, the 
refraction and parallax, in right ascension and declination, will 
be obtained, t, u, are two handles to a Hook's joint at x, x> 
which, turning an endless screw at w, w, give a gradual mo- 
tion to the telescope in right ascension or declination ; and 
this motion can at any time be restrained by a clamp at q» 
The handles t, u, are hung on to any part of the instrument, 
by means of the line and wire v, v, and are thus kept within 
the observer's reach, r and s are two microscopes, placed on 
opposite sides of the circle QR, and at right angles to the 
line of sight of the telescope, of use only when the plumb 
line is used in preference to the level /, m, above described, 


of the Equatorial Instrument. 81 

either for adjusting the instrument, or observing a meridian 
altitude, y and % are thin perforated brass plates, attached to 
the cover that goes on the object glass, and, by occasionally 
turning them over it, change the aperture to or ^ The 
cross wires, of which there are 3 vertical, and 1 horizontal, 
within the eye tube S, have all the requisite adjustments by 
screws, &c. as in a common transit instrument, and are en- 
lightened by night, by a lamp fixed near to one end of the de- 
clination axis U, viz. that opposite the end V; but this part of 
the apparatus is hid behind the axis and the telescope, except 
the weight i, which is a counterpoise. This lamp throws a 
light through the conical axis, which is perforated at that end 
on purpose, on a speculum in the centre of the telescope, 
placed at \ right angles to the axis of the object glass, and 
from thence reflected to the cross wires. This speculum, 
which is an elliptical diaphragm, is perforated to permit all the 
rays from the object glass to pass unobstructed to the eye. 
This contrivance has been mentioned by Mr. Vince. (Practi- 
cal Astronomy, p. 80.) From what has been already de- 
scribed, it must now be evident that if the principal, or po- 
lar axis, as it has been called, LN, be elevated to the lati- 
tude, and adjusted to the meridian of the place, if the line of 
sight of the telescope be at right angles to the axis V U, and 
this latter at right angles to the polar axis LN, the brass 
circle 14 and 15 will correspond with the equator in the 
heavens, and the circle QR will become an horary circle ; 
viz. that if the centre of the wires, in the field of the tele- 
scope, be directed to any celestial object, on QR will be had 
its declination, and on 14 and 15 its distance from the meri- 
dian, from whence, by knowing the hour, the right ascension 

M 


MDCCXCIII. 


82 Sir George Shuckburgh’s Account 

will be obtained,*' and consequently its true place in the 
heavens. 

(14.) Before I proceed, it may be necessary to say some- 
thing of the remaining parts of this apparatus, such as are 
either necessary to it, or concomitant in the use of it. These 
are, 1. The lamp to illuminate the cross wires. 2. The re- 
fraction piece. 3. The plumb line. 4. The moveable roof. 
5. The regulator. 6 . The meridian mark. And these will 
be best understood by inspection of the plates, where Tab. X. 
figure 1, represents the lamp fixed to the farther end of 
the declination axis. AB is the brass case or lantern, sus- 
pended on two centres C and D, within the frame E and F, 
which is attached to the pillars of the equatorial (IK, GH, 
and that one hidden behind E F ) by the cylindrical braces a, 
b , c , d. e is the lamp or vessel containing the oil, swinging 
upon the centres/ and g, at right angles to C and D ; and by 
means of this cross axis, and the counterpoise h, the lamp is 
kept constantly in an upright position, whatever may be the 
situation of the declination axis. G is a chimney to carry off 
the smoke from the instrument, and prevent its heating it. 
1, is a convex lens, that collects the rays from the flame 
upon the extremity of the declination axis, U, V, which, be- 
ing hollow, conveys all the light to the perforated speculum 
before mentioned, within the centre of the axis and of the 
telescope ; and this is assisted by another convex lens at the 
end of the axis, before which occasionally is screwed a pale 
green glass, of which there are three, of different shades, to 
temper the light of the lamp, if necessary, to the light of the 

* The adjustments which T have just now mentioned, together with some others, 
will be duly explained in their proper places. 


of the Equatorial Instrument. 83 

star that is to be observed. This light, as was said before, 
being reflected down the tube to the wires, the stars are seen 
upon a beautiful pale green field, the wires appearing black. 
The centre D being of necessity full two inches in diameter, 
in order to admit of the aperture and lens i, rests on three fric- 
tion wheels, and by this means the motion is as easy as on the 
centre C. At k, /, ?n, n, is a small sliding door, to close up 
the lantern from the wind, but which is here removed to shew 
the inside. 

(15.) Tab. X. figure 2, represents the refraction piece. 
AB is a portion of the telescope; C the eye tube; a, b, c , 
a divided semicircle; d its nonius fixed to AB, shewing the 
angle of the horary and verticle circles ; e , a small spirit 
level, attached to the plate on which this semicircle is en- 
graved, and moving with it by means of the screw f which 
turns a pinion, that works in a toothed wheel, that turns the 
whole plate, together with the exterior eye tube, round its 
centre, but without moving the tube that carries the cross 
wires. From hence it may be understood, that by turning 
the screw f till the level e stands true, the index d, which 
represents a point in the horary circle, will mark how much 
the division zero, (0) which represents the vertical, is in- 
clined thereto. /, k , is a small quadrant of altitude, that, by 
means of the level g, and screw and pinion h, turning on a 
centre at m, gives the elevation above the horizon of any ob- 
ject in the field of the telescope, i, is a small aperture through 
which a key is fixed on, to give a lateral motion to the wires 
to adjust them ; and near / is another screw, to adjust them 
parallel to the equator and declination circle. 

Ms 


84 Sir George Shuckburgh’s Account 

(16. ) Tab. X. figure 3, represents the plumb line and its 
frame ; it is about 5 feet long, and suspended to the roof of 
the observatory by the two hooks a, a. AB is a hollow brass 
tube, to protect the plumb line from the wind ; the line or 
wire is fixed at the top near b, and sustains the plummet in a 
glass of water at C. b and c, are two adjusting screws, mov- 
ing a sliding plate at right angular directions, to which is 
fixed the upper end of the plumb line, d is a screw, that by 
means of a pinion moves a rack e, e, to depress or raise the 
glass of water, and thereby support the plummet, (when this 
apparatus is moved about from one side of the instrument to 
the other) and prevent the wire being broken, and, by depress- 
ing it, to enable the plummet to play free, when it is to be 
used. At A and B are two apertures, at 4 feet distance, cor- 
responding with the two microscopes, covered on the back- 
side by pieces of transparent ivory, in order to exhibit an 
agreeable field of view, to observe the coincidence of the 
plumb line with the cross wires in the microscopes. 

(17.) In Tab. XI. is seen a section of the building 
in which this instrument is placed. As the equatorial is 
a machine calculated to observe the heavenly bodies in every 
part of the hemisphere, so it became necessary to construct a 
chamber, with windows opening to every quarter, north, east, 
west, and south ; and to any degree of elevation above the 
horizon. With this view I erected a building, or small turret, 
within my house, at Shuckburgh, in Warwickshire, see Tab. 
XI. where a, b, c, d, represent a section of this room, be- 
ing about 154- feet square, containing the equatorial AB, rest- 
ing on its supporters CD. s, 0, p, r, q , t , is a hollow conical 


of the Equatorial Instrument. 85 

roof,* moveable round its axis upon six friction rollers, of 
about 4 inches in diameter, two of which are seen at s and t. 
The base of this cone consists of an iron ring, about 1 1 feet in 
diameter, and 3 inches wide ; the upper part of the cone at 
s, is terminated by another iron ring 2 \ feet diameter ; and 
these are connected by 12 iron ribs, or rafters, in the direction 
of s, s. Over these rafters lie two coats of extremely thin deal 
planks, not more than inch in thickness each, crossing each 
other in transverse directions of the grain of the wood, and 
over these a covering of copper, of about the thickness of a 
shilling. Over the copper, on the outside, are three good coats 
of white paint, and the wood withinside is lined with stout 
canvas, well painted also ; so that the whole roof is as move- 
able and as light as possible, not more than 200 or 3001b. 
weight, and withal very strong. At s and s, is an aperture, 
in the roof, of about one foot wide, which is opened or co- 
vered, suitably to the occasion, by the two doors 0, p. r is 
another door, (in the plate) open ; by means of these three 
doors, all opened very readily by iron rods withinside, a 
prospect is given of the heavens from the horizon to the ze- 
nith, and even to io° beyond it. q is another aperture, about 
9 inches long and 4 wide, covered occasionally by a shutter z. 

* As I flatter myself that I have now executed what the very celebrated Abbe 
Boscovich seems to have had in view, in the 14th opusculum of his fourth volume of 
Opera pertinentia ad Astronomiam, &c. I cannot restrain myself from citing the 
passage, wherein, after describing the use of the small equatorial, he says ; “ Apparet 
“ igitur egregius usus machine etiam mobilis. Verum machina parallactica metallica 
“ cum circulo, et semicirculo, satis magnis, ac telescopio acromatico, et satis bono mi- 
“ crometro filari, collocata firmiter in turri habente tectum mobile, esset instrumentum 
“ usus immensi et expeditissimi, ac incredibilis ad astronomiam cum maximo fructp 
<£ excolendam utilitatis.” p. 309. 


S6 


Sir George Shuckburgh's Account 


This little window affords a constant view of the pole star in 
its whole revolution, if the sky be clear, and consequently an 
opportunity of comparing a transit and altitude of any star to 
the southward directly with it ; and, by moving the conical 
roof round, any part of the sky may be exposed to the tele- 
scope. The rollers * s, t, roll upon a surface of lead, melted 
and cast into a circular groove in the timbers at EE, and 
planed truly horizontal. Besides the apertures already de- 
scribed in the roof, the room is enlightened by two windows 
to the south-east, and north-west; and also by two oval lights 
in the side of the cone, nearly east and west, and by a third in 
the zenith at r. v, w, is a platform on the outside of the 
cone, covered with lead ; of use in examining the roof, 
and cleansing it in time of snow, See. y and x are iron ba- 
lusters, very necessary on such occasions, with the iron rail 
at top at x placed obliquely, in a plane tending to the centre 
of the instrument, in order that the least possible light from 
any object may at any time be lost to the object glass. C is 
one of the iron bars passing through the wall of the building, 
fixed by a collar and nut on the outside, and resisting the 
pressure of the instrument, whose weight, without the sup- 
porters, is full 300 lb. against the support D. e,j, \ l, and g, b, 
n, are two of the side walls of the building, rising 40 feet 
above the ground, and serving as butments to the arch /, m, w, 
which is farther strengthened by a square frame, of heart of 
oak timber, 9 inches by 6 inches, let into the wall at 5, 6 , 
held together by iron bolts, and going round the building, 

* Besides these rollers, whose axes are horizontal, there are 3 or 4 other rollers, upon 
a vertical axis, exterior to, and bearing against the ring that constitutes the base of the 
cone ; by this means they keep the centre of its motion always in the same place. 


of the Equatorial Instrument. 87 

This arch is filled with solid masonry * to the height i, k, 
into which, as upon a plane brick floor, the iron frames that 
support the instrument are firmly fixed with plaster and 
lead at 1, 2, and 3, 4, and hence the instrument seems as 
steady as upon a rock, b, d, is a boarded floor, that has no 
connection whatever with the instrument, or its supporters. 
u, u, are the two mahogany cases that cover up the apertures 
in the floor, and serve as bases to the supporters C and D, 
but do not tcuch the iron frames within ± inch ; so that any 
yielding of the floor, b, d, by passing to and fro thereon,, 
communicates no motion whatever to the instrument. 

(18.) To the north-east wall-f c, d, by means of timber 
laid into it, and long screws, is firmly fixed the clock, or 
sidereal regulator, but so as to have no communication with 
the floor. As it is peculiar in its construction, it may de- 
serve some notice. Whereas most astronomical clocks shew 
sidereal time in hours and minutes, which is afterwards, in the 
course of computation, reduced to degrees and minutes ; this 
machine shews the degree and minute of the equator, that is 
upon the meridian at any given instant, directly without reduc- 
tion. This is of considerable convenience in observations, out 
of the meridian, with an equatorial instrument ; inasmuch as 
the equatorial circle and the clock, by these means, speak the 


* The bricks of this arch were laid dry, and then grout, consisting of gra- 
vel and hot lime, was poured upon them ; when the arch had stood two years, the 
haunches were filled up with bricks, laid in mortar. I mention these circumstances, 
as attention to them may be of use upon a similar occasion, whenever it shall be ne- 
cessary to erect an arch bearing so great a weight, viz. near 30 tons, upon such slight 
buttresses. 

f The walls of this room do not correspond with the cardinal points; the section 
here given having an aspect 53 0 S. east. 


88 Sir George Shuckburgh's Account 

same language. For this purpose the vibrations of the pen- 
dulum are only y of a common pendulum, = 10" of space ; 
and the index that is carried round immediately by the pen- 
dulum, viz. on the same arbor with the pallet wheel, in one 
revolution describes 10' of sidereal space ; the next index from 
the centre of the dial plate shews the degrees, and every 10th 
minute, making one revolution in io°. And lastly, the de- 
cades of degrees, from 1 to 3 6, = 360°, are shewn through an 
opening in the dial plate, which in some clocks is ap- 
propriated to the day of the month. But perhaps this will 
be better seen from inspection of the plate (Tab. XII.) 
wherein the hands are so placed as to indicate 147 0 14' 10". 
The small hand (it may be perceived) has two sets of figures 
round its circle, the one shewing the minutes, and every 10th 
second, the other the number of beats from o to 60, and this 
latter enumeration is what alone can be attended to in the 
observations ; that is, the degrees and every 10th minute are 
set down in the journal immediately from the indexes, and 
the subdivisions below io' are set down in beats of the pen- 
dulum, reckoning from o to 60, and reduced afterwards at lei- 
sure. The pendulum, only 1 7 inches in length, is a compound 
gridiron composed of 5 rods, of which 3, viz. the centre and 
two exterior, are of iron, and the two next to, and on each 
side of the centre, are compounded of silver, brass, and zinc. 
The weight of the pendulum ball is about 6 pounds, and that 
of the clock weight 32. The spring, by which the pendulum 
is suspended, is said to be so constructed as to produce cy- 
cloidical arcs of vibration ; but my reliance upon this con- 
trivance is not very perfect. The two chief arbors are 
jewelled, the pallets are rubies, and the axis of the principal 


of the Equatorial Instrument . So 

great wheel moves on friction wheels ; and I believe every 
care has been taken, that the experience of one of the first 
artists of this kingdom * could suggest, to render it a com- 
plete piece of mechanism. It goes five months with once 
winding up ; and, from the experience I have hitherto had, 
does not seem to vary its rate between winter and summer 
more than equal to three seconds per day, sidereal time. 

(19.) All, I believe, that remains for me to mention, in 
this part of the account, is the meridian mark. (See Tab. 
XIII.) A,B,C,D,E, is a solid brick pier, erected at the dis- 
tance of 2970 feec from the centre of the observatory ; 
8 feet high, 9 feet wide at bottom from A to E, and 4 feet 
wide at top from B to C ; 1 foot 6 inches thick at top from 
C to D, and 2 feet 3 inches at bottom. F is an iron box, 
8 inches square, and 1 foot high, exclusive of the top, or 
chimney ; within this box is placed one of Argand's patent 
lamps, which shines through a circular aperture, of about 
inch, in the front of the box, and exhibits the appearance 
of a fixed star to the naked eye by night ; but the aperture 
being covered by a semitransparent piece of glass, ground 
rough on one side, transmits a steady uniform light, that 
through the telescope resembles the disc of a small planet 7"^ 
in diameter. By making the wire in the telescope, which is 
only in diameter, bisect this circular light, the in- 
strument may be very nicely adjusted to the meridian, indeed 
with so great precision, that I think an error of one second 
cannot be committed. Around this glass aperture, which by 
clay appears perfectly black, is painted a circle of black, (on a 
ground of white) whose external diameter is 3 inches, and 

# Mr. John Arnold. 

N 


MDCCXCIII. 


^0 Sir George Shuckburgh's Account 

consequently subtends an angle of 18". The bisection of 
this last is made use of by day, and although, it is true, it is 
rather larger than is necessary for a meridian point , yet it was 
convenient it should be so, to render it visible in the dark 
winter months, if there was the least vapour rising from the 
ground. Yet with all this, no error need be apprehended ex- 
ceeding 2", equal to only of a second of time, nor that, un- 
less the image should be greatly agitated by the vapours. 
This mark is not only of use to find the meridian, but also 
to determine the horizontal point, when once the angle of it 
above or below the horizon is ascertained ; and, by comparing 
the meridian altitude of any object with this point, its declina- 
tion may be had, almost as nearly as by the level or plumb line. 

I ought to have mentioned before, that the box F is move- 
able upon the plane B,C, by means of an iron frame on 
which it slides, and screws to adjust it finally to the true 
meridian. 

Although there can be no great danger of a solid pier, like 
the above, erected on a foundation four feet deep, being 
likely to move, yet this doubt, if any should occur, may be 
examined by a plumb line a , b, suspended from a, and play- 
ing near a corresponding mark, on the top of a post driven 
into the ground at c. G, E, are steps to ascend to light 
the lamp, or take it in and out at the door d. The whole 
is surrounded by high pallisadoes, to protect it from the acci- 
dents of cattle, or curiosity. 

(20.) Having thus particularly described the various parts 
of the equatorial, I trust in a manner sufficiently intelligible 
to any person a little conversant with astronomical instru- 
ments, it may be proper to say something of its precision ; 


of the Equatorial Instrument, tji 

for without some competent knowledge of the accuracy of its 
parts, it is in vain to attempt to adjust them, and still more 
so to use them with any degree of satisfaction.- And here the 
chief objects of inquiry have been the accuracy of the divi- 
sions ; the sensibility of the levels ; and the power of the tele* 
scope. I shall begin with the levels ; and first with the axis 
level, P, k, the parts of which may be seen at figure i, 
Tab. XIV. where 1, 2, represent the extremities of the axis 
of the circle of declination ; A, a section of the tube of the te- 
lescope ; 3, 3, the level tube, resting in the cocks or sup- 
porters, 4, 4, and 5, 5, and turning on an axis d, e ; on one end 
of which e, is a toothed wheel g, moved by a small pinion f. 
turned by the screw head b ; and at a, is an adjusting screw 
to bring the level parallel to the axis 1, 2 ; at c is another, to 
bring the level parallel to its moveable axis d, e ; h, is an 
adjusting screw, at right angles to C, to bring the tube of 
the level parallel to its axis d, e ; i, is another screw, to 
make this axis parallel to the axis 1, 2. All these, as well as 
every other adjusting screw throughout the instrument, have 
chamfered heads, with their circumferences divided into 10 
parts, and the value of each ascertained ; so that, by turning 
the screws a whole, or any part of a revolution, the angle of 
motion given to any part may be known. The use of this is 
obvious ; but the degree of convenience is only known to such 
persons as have been conversant with these nice adjustments. 
k and /, are two moveable indexes, to be set to each end of 
the bubble. The tube of this level is about 14 inches long, 
and the curvature of it such, as that by giving it an inclina- 
tion of 15", the bubble moves about ~ inch, and the third or 
fourth part of this space is plainly discernible, so that no 

Ns 


92 Sir George Shuckburgh's Account 

error exceeding 3 or 4" need be apprehended, if proper care is 
taken. 

The swinging level l, m, fixed to the tube of the tele- 
scope, for the purpose of taking declinations, is unground, and 
of very superior sensibility, as it ought, having been selected 
expressly from a great many yards of glass tube, in order to 
get one with a proper flexure ; and such has been the success of 
this care, that a change of inclination of this level of one single 
second, moves the bubble nearly ~ of an inch, certainly more 
than ~* This, I am inclined to believe, is the greatest sen- 
sibility that has ever yet been attained by a level : it is at the 
same time somewhat inconvenient, since it sometimes will 
require two or three minutes time to settle to its true point, 
it moves so slow. An error, however, of more than a second 
need seldom be apprehended, which I conceive is as much as 
could have been expected from a plumb line of a length equal 
to the diameter of the circle. The . bubble of this level is 
about 7 inches long, but this varies with the temperature ; and 
I have experienced that with about 28° of heat the bubble 
contracts one inch in length ; this makes it very necessary to 
be attentive to the index at each end of the bubble. The 
parts of this level may be seen at figure 2, Tab. XIV. 
A,B, is one side of the tube of the telescope, whereon are 
firmly fixed two upright supporters, or cocks, C, D, and E, F ; 

* If the motion of the bubble be taken to be even 0,2 inch, it will be found that the 
radius of curvature is more than 1 100 yards ; and, supposing the length of the level 
— 12 inches, it will only comprise, from one end to the other, an arch of 1', and the 
versed sine of 30", in this case, would express the depressure of the tube at its extre- 
mities below the centre of the level about half T -<™ of an inch. 

The curious ground level, for adjusting the axis of the transit instrument at the ob- 
servatory at Greenwich, moves, as I have been informed, about 3-5 inch for 1". 


93 


of the Equatorial Instrument. 

in which the level G, H, I, about 12 inches long, swings upon 
two conical centres a , i, truly turned, of polished steel. G I, 
is an hollow brass tube, about i inch in diameter, containing 
within it a steel triangular axis, one extremity of which is 
terminated by the conical centre a, and, by means of a spiral 
spring winding round the axis, is made to contract its length 
by pulling the trigger g, towards I, by which means the 
point or centre a, retires within the tube G I ; so that the 
two centres may easily be released from the steel pivots 
wherein they play, and the level may be reversed, if neces- 
sary, to adjust it. It is evident that the axis a, i, should be 
parallel to the line b, b, which may be taken for a tangent 
to the curvature of the tube at k, and this is procured by 
the capstan headed screw c; it is also necessary that this 
same axis should be parallel to the line AB, or rather to the 
line of collimation of the telescope, in a north and south 
direction, and this is obtained by the capstan screw d. 
Finally, it is expedient that this axis be parallel to the line 
of collimation, in a direction east and west ; and this is ef- 
fected by the screw h. e, e, are two indexes to mark each 
end of the bubble, and, being fixed to the two concentric 
sliders/,/, which embrace y of the circumference of the tube 
GI, are moveable any where at pleasure, h is one of two 
screws, the other being opposite and out of sight, for ad- 
justing the axis a, i, parallel to the line of collimation, east- 
ward or westward, as has been said, and at right angles to 
the declination axis. I proceed next to the divisions. 

(21.) The superior advantages of an entire circle/ over a 

* Vide Observations Astronomicce Annis 1781, 1782, 1783, institute in Observa- 
torio Regio Hauniensi, auctore Thom a Bugge, Hauniae, 1784. Quarto. Cap. 5. 


94 


Sir George Shuckburgh’s Account 


quadrant or sextant, for astronomical purposes, are almost in- 
credible to a person that has not considered the properties of 
a circle, and so great, that I am much surprised it has not 
been brought into more frequent and earlier use. For, in the 
first place, the error of the centre, which so constantly takes 
place in quadrants, is entirely done away ; secondly, the small 
error in each individual division is discovered, so that what- 
ever be the skill of the artist, the observer is under no obli- 
gation to rely upon it, but can examine the whole himself. 
The method I proposed was this, to make the index wires in 
the opposite micrometers an exact diameter to the circle, 
and then to observe whether each division corresponded with 
its opposite one, and if any difference, to set it down ; these 
differences I expected to find somewhere = o" o, viz. in the 
diameter passing through the true centre of the circle, and 
the centre of the pivot, round which the machine revolved, 
and at right angles to this they would be at a maximum. 
The greatest quantity of this eccentricity, and the place 
where it lay, being ascertained, it would be easy to deter- 
mine what it was in any other place ; for this eccentricity, in 
any given part of the circle, would be as the co-sine of the 
distance from that point where it was at a maximum ; and 
if, on this principle, a table was constructed, giving the eccen- 
tricity at every degree round the circle, the numbers in this 
table might be compared with the actual observation of the 
eccentricity, by the microscopes all round the circle, and if 
the quantity in the table did not every where agree with that 
found by experiment, the difference would be the actual error 
of that individual division ; and in this manner the whole 
might be examined, every error detected, and a memoran- 


95 


of the Equatorial Instrument. 

dum made of it. With this intention, and a full expectation 
of finding the eccentricity = 8" or 10", I set to work to exa- 
mine the circle all round, having previously determined the 
diameter of the points in the arch to be about 21", and the 
thickness of the wire = 12". It is true, the points were not 
all exactly of the same size, nor could it be expected, but in 
general it might be concluded, that when the wire equally 
bisects a point, the segment on each side of the wire is about 
= 4" : so that an error of 1" in the bisection can never be 
committed, with a tolerable light and reasonable care, the mi- 
croscope magnifying 16 or 18 times. I placed the moveable 
wire of the east microscope so as to bisect the division 360°, 
and then, by repeated trials, made the moveable wire of the 
west microscope bisect the opposite point of 180° ; in which, 
taking a mean of three or four observations, I could not err 
more than a few tenths of a second. The index of the mi- 
crometer screw being then carefully adjusted to zero (0) of 
the divisions of the head, I made every 10th degree of the 
circle pass under the micrometer wire of the east microscope, 
which wire might now be considered as fixed, and then noted 
whether the opposite division was under the moveable wire 
of the west microscope ; if not, I wrote down the difference, 
after three or four times reading off. The result of these ex- 
periments may be seen in the adjoined table. Where 

The 1st column shews the point, or division, that was 
brought under the wire of the east microscope. 

The 2d column shews the want of coincidence, or how 
much the opposite point disagreed with the wire in the oppo- 
site microscope, at each reading off. 

The 3d column gives the mean difference, and is = double 


9® Sir George Shuckburgh's Account 

the error of the centre -j- the sum of the errors of the two 
divisions. 

The 4th column shews the difference of the mean reading 
off from the extremes, and may be considered as the greatest 
actual error in reading off these observations. 

The 5th column contains the numbers in the 3d column 
corrected, by subducting o".g, a quantity which, it was 
found, upon taking the mean of all the numbers in the 3d 
column, the opposite or west micrometer was tco forward 
upon the circle, viz. did not make a perfect diameter, but ex- 
ceeded it in the order of the degrees by o".g. It will be 
observed that this quantity, from the three first series of ob- 
servations of the points 360, and 180°, seemed to amount to 
o".6 ; this difference is inconsiderable. The numbers then 
in the 5th column, thus corrected, will express the true dif- 
ference between the opposite divisions, if the wires in the 
microscopes had described a true diameter. 

The 6th column gives the half of the difference just men- 
tioned, and is = the simple error of the divisions. 


of the Equatorial Instrument, 

Table of the Divisions of the Equatorial Circle. 


97 


i 

2 

3 

4 

5 

6 

East 

micro- 

West mi- 

Mean 

diffe- 

Diffe- 
rence of 
the mean 

Column 
3d cor- 


croscope, 

Simple 

scope. 

difference. 

rence. 

from the 

rected. 

error. 




extremes 



0 • 

O 

// 

It 

It 

it 

360 0 

180. -1 







II 

-f 0,0 







1,2 

>• 

+ 0,7 

0-5 

— 0,2 

— 0,1 


°,7 






1,0 

0,6-i 






560° 0' 

+ °>41 






epeated 

0,8 


+ 0,7 

0,2 

— 0,2 

— 0,1 


0,9 J 






560° 0' 

+ 0,8-j 






epeated 

0,2 1 
0,0 | 

>■ 

4 0,4 

0,4 

-o,S 

— 0,25 


0,5 J 






ean of these three 

4- 0,6 




0 / 

O 





10 0 

190. 







II 

+ i >5 

y 

4- 2,3 

0,8 

4 1,4 

4 0,7 


2,6 





2 . 7 J 






20 0 

200. 'i 







4- 1,0 


4- 0,9 





o ,7 


0,2 

0,0 

0,0 


1,0 J 






30 0 

210. 







+ 3 »i 







4 > 1 

> 

+ 3>8 

0,7 

+ 2,9 

+ 1,45 


4,0 







3 > 9 J 






40 0 

220. -1 







+ 4 jZ 

3>9 


4 - 4 * 1 

0,2 

4 3,2 

4 - 1,6 


4 > 2 , 






30 0 

230. 
-f- 1,6 
i >5 

\ 

4 M 

0,1 

-j- 0,6 

4 0,3 


Ij 5 , 

I 





60 0 

240. 
4- 2,8 
3,6 

\ 

4 3»4 

0,6 

+ 2>5 

4 1,25 

% 

3 6 , 

1 





70 0 

250. *n 







+ 3’2 
3 >o 


4 2,7 

o ,7 

4 1,8 

4 0,9 


2,0. 







East 

micro- 

scope. 


8 o O 


90 O 


IOO O 


no 


1 1 1 


1 20 


*30 


140 


150* 


160 


170 


West mi- 
croscope, 
and 

difference. 


260,, > 

+ 3 ’4 I 

3.5 I 

3>8J 

270. I 
+ °,8 1 
o,s r 
1 > 7 J 
280. 

+ '*[ 

2,2 f 

2,4! 

29 °-*q 

+ O >7 1 

~ 1,2 f 

- 07 J 

291. . 
+ 0,8 

1.5 I 

30°. ^ 

- °>5 I 

- o,7 f 
+ o,5j 

3 IO * 'i 
+ 0,7 I 

- 0, 5 [ 

- i,oJ 

320- ] 

- 2 ,7 I 

- 1,6 f 

33 °- q 

- °>\ l 
4 0,7 f 

+ 1 >°J 

34 °- q 

- 2,2 \ 

-1,2 

- 2,0 j 

35 °- 1 

- 1,6 

- 2,2 

- i »7 


Mean of all 


Mean 

diffe- 

rence. 


4 3 < 6 


+ «,i 


+ 2,0 


-0,7 


+ 0,9 


— 0,2 


- 0,3 


— 2,2 


+ °,4 


- 1,8 


— 1,8 


4 

5 

6 

Diffe- 
rence of 
the mean 
from the 
extremes 

Column 
3d cor- 
rected. 

Simple 
error. * 

II 

II 

a 

0,2 

4 2,7 

4 1,35 

0,6 

4- 0,2 

4 0,1 

0,5 

4 1,1 

40,55 

1,0 

4 1 ,6 

4 " 0,8 

0,6 

4 - °,o 

0,0 

0,5 

— 1,1 

-0,55 

1,0 

— 1,2 

— 0,6 

0,6 

- 3 U 

- 1 ’55 

0,8 

-0,5 

d 

1 

0,4 

- 2,7 

- 1’35 

0,4 

- 2 .7 

- i ,35 


— 0,9 0,53 


Those with * affixed are doubtful or bad points, 

o 


MDCCXCIII. 


g8 Sir George Shuckburgh's Account 

From inspection of the preceding table of observations it 
will readily appear, that I was much mistaken in my ex- 
pectation of an eccentricity of 8 or 10", for that, in truth, 
there seemed to be no fixed cause of error ; and that therefore 
the error of the centre had little to do in occasioning those 
differences in the opposite microscopes, which only once 
amounted to 4", and this in fact was double the error of 
the centre added to the sum of the errors in the two op- 
posite divisions, together with the error of twice reading 
off ; and that the simple error never exceeded, and but once 
amounted to i",6. This being the case, I think it fair to 
conclude, that the eccentricity never amounted to any sen- 
sible or measurable quantity, viz. never exceeded 1",* and 
that consequently all the variety we see, in the west or oppo- 
site microscope, arose from the error of the divisions, ine- 
quality of the points, imperfection in reading off, or a little 
play in the screw of the micrometer. But, as all these toge- 
ther never but once amounted to 2", I think it may fairly be 
presumed that that is the greatest error that will arise, in any 
observation made with this circle, when only one mi- 
croscope is used, and that probably only half that error will 
take place. 

* How extremely small a quantity this is, may be seen by considering that, on a 
radius of two feet, an arc 

of 10' amounts only to - - - 0,0698 inch. 

of 1' - - - 0,0070 

of 1" to { — in round numbers to about inch.) 0,0001 16 
Viz. to about 8 times less than the minimum visibile to the naked eye. This I 
reckon, with my own eye, at 8| inches distance, is about inch ; but then it must 
be considered that the microscopes magnify 16 times, and will therefore render a space 
visible that is inch, or about = o"f, which we shall soon find to be the fact. 


99 


of the Equatorial Instrument. 

After this examination of the equatorial circle at every 10°, 
I did not think it necessary to proceed in the examination of 
each degree, and still less of every 10', as I had intended. I 
therefore quitted this, and went to the declination circle, 
which underwent the same trial. The results of which will 
be seen in the adjoined table ; the divided arch of the decli- 
nation circle being turned towards the east. 


100 


Sir George Shuckburgh's Account 


Table of Observations of the Divisions of the Declination Circle. 


Mean 



Farthest 


Diffe- 



Farthest 



Diffe- 


ist micro- 

microscope 

Mean 

rence of 

Simple 

1 st micro- 

microscope 

Mean 

rence of 

Simple 

scope next 

next the 

diffe- 

the mean 

error. 

scope next 

next the 


diffe- 

the mean 

error. 

the eye. 

objectglass 

rence. 

from 


the eye. 

objectglass. 

rence. 

from 





extreme. 

- 





extreme. 


Div" from 

S. pole. 

// 

II 

// 

90° 0' 

90° o'" 


n 

// 

n 

0 ! 

0 





// 





IO o 

10 0 





— 1,0 

► 

-0,7 

°,5 

0 

1 

// 

II 





— 0,2 




4 0,2 

- 0,3 l 

— 1,0 f 

— 0,1 


— 0,05 


— 0,8 





— 0,2 

— 0,9 

ICO 

100 





- 0,3 

+ °>3 

1 + 

0 0 

VsJ 

L_ 





+ 1,9 

+ °,4 
+ 0,5 

► 

+ °j 9 

x,o 

+ °»45 











0,0 






4 1,0 J 





20 O 

20 o'] 




1 IO 

1 10 






— 0,1 1 

-<M f 

— 0,6 

0,6 

-0,3 


+ 0,5 

+ o } 6 


+ 0,3 

0,5 

+ 0,15 


— 1,2 J 





— 0,2 J 






30 0^ 

-0,5 1 

-n 5 r 

— 0,7 J 




120 

120 





3 ° 

— 0,9 

0,6 

- ° 4 S ' 

130 

-0,5 
+ o ,7 
+ 0,4 

130 1 

► 

+ 0,2 

°>7 

+ 0,1 

40 

40 CT1 
— 1,0 1 
-0,9 f 

- i >3 

o ,7 

— 0,65 


+ 1 1 

poo 

ONVO 

> 

— 0,4 

o >7 

— 0,2 


— 2,oJ 




I4O* 

I4O 
-f- 0,2 


+ 0,3 



1 5°* 

1 

50 O-V 
-2,6 1 

-3 >7 r 
— 2,8 J 

-3,0 

°,7 

- ns 

I5O* 

— 0,1 
+ 0,7 
150 ■) 

y 

0,4 

+ 0,15 







— 0,4 





5 2° IO' 

5 2 ° IO ' 1 





-0,3 

>■ 

— 0,4 

0,1 

— 0,2 


+ 44 l 
+ 5> 2 \ 

+ 4>7 

0,5 

+ 2 >35 

l6o 

-°, 5 j 

160 






+ 4 . 5 J 





— 0,1 



0,6 


60* 

6 °\ rl 





+ 1,2 
-f 0,2 

> 

+ 0,7 

+ 0,3 5 


- »«5 l 

— 1,0 j 

+ 04J 

-0,7 

0,8 

-o,35 

170 

+ °> 7 . 
170 


+ 0,6 

0,6 


7 ° 

70. -1 





+ 04 

> 

+ 0,3 

- 14 l 

— 2,0 f 

— 2,0 

0,6 

— 1,0 

l8o 

+ °>3 J 

180 






-2,6J 





+ 04 


+ °>5 


+ 0,25 

80* 

80. 1 

+ 2 4 L 
+ 3 >i f 

+ 2,7 

0,4 

+ *>35 


+ 0,6 
+ ° 4 . 

> 

0,1 












1 ■■ 


2j6j 




Mean 

of all 


+ 0,04 

o ,57 



* Denotes a doubtful or bad point. 


tot 


of the 'Equatorial Instrument. 

From the preceding table of observations of the declination 
circle it appears, that these divisions were very little, if any, 
inferior in accuracy to those on the equatorial circle. And, 
finally it appears, that the errors, and probability of error, 
were as follows ; viz. in the equatorial circle, from 22 cor- 
responding observations of opposite divisions, 


Obs n . 


In 0, the error amounted to 2" 

therefore the probability 



against this error was 

5. - about i\ 

- 

- = 3 t to 1 

8. 1 

- 

- =2 to 1 

14. - - about o\ 

- 

- =1 to 2 

And in the declination circle, from 19 corresponding ob- 

servations of opposite divisions, 



Obs". 

therefore probability against this error. 

In 1, the error amounted to about 

2" 

= 18 to 1 

3 - 


= 5 to 1 

4 - 

1 

1! 

r-f 

O 

M 

8. 

0— 

2 

= 3 to 2 

Therefore from 41 double observations on both circles, 

Obs". 



In 1, the error amounted to 

2" 

viz. =40 to 1 

8. 


11 

r+ 

O 

12. 

1 

= H to 1 

22. - 


= 1 to 1 

We may conclude, therefore, 

that 

in both circles no error 


of more than 2" need be apprehended from the centre, and 
from the divisions taken together ; and that in general it will 
probably not exceed 1", on condition that the micrometer 
screw head is read off thrice, which in some observations 


log 


Sir George Shuckburgh's Account 


may be done, if necessary. Lastly, from taking a mean of all 
the numbers in the 4th column, it seems the probable error, 
in reading off the divisions, is only o ",53 in the equatorial 
circle, and o",^y in the declination circle. This source of er- 
ror may therefore be put at o"\ ; so that if one quadrant 
only of the circle should be made use of, viz. only one mi- 
crometer, and that only once read off, it is probable that no 
error of more than will be committed. I mention this, 
because it will sometimes happen that only one such observa- 
tion can be made ; but where sufficient leisure will allow the 
reading off both the microscopes, this small error of will 
probably be halved ; and if the declination circle be turned 
half round, and the observation repeated, in the same man- 
ner, upon the two remaining quadrants of the circle, as is 
done (we shall presently see) when the line of collimation is 
examined, this error will probably be quartered, or reduced to 
less than o"±. 

After the very rigorous examination the divisions of these 
two circles have now undergone, and from the general know- 
ledge that I have had opportunities to obtain of the state of 
practical astronomy in different countries ; and when I con- 
sider that the celebrated artist, the late Mr. John Bird, 
seems to have admitted a probable discrepancy in the divi- 
sions of his 8 feet quadrants, amounting to * 3", I think I am 
entitled to believe that the accuracy of these divisions under 
consideration is hardly to be equalled, and still less to be ex- 
celled, by that of any astronomical instrument in Europe ; 
and, from the unexampled diligence and care, with which the 
skilful artist Mr. Matthew Berge, workman to Mr. Rams- 

* See Mr. Bird’s Method of constructing Mural Quadrants. London, 1768. 


of the Equatorial Instrument. 103 

den, has executed them, I feel myself bound to bear this tes- 
timony to his merit. 

(22.) It remains that I now say something of the power of 
the telescope ; for it is to little purpose that the divisions be 
accurate, or the levels sensible, unless the force of the tele- 
scope be such as to correspond with the sensibility of the 
one, and the accuracy of the other. The object glass is a 
well corrected double achromatic, whose joint focus is 65 
inches, with an aperture of 4,2 inches. The telescope is fur- 
nished with two sets of eye glasses, one single, the other 
double ; of these latter there are 6, of different magnifying 
powers, from 60 to 360 times ; of the former there are 5, 
with powers from 150 to 550. To these may be added a 
prism eye tube, with a power of about 100, for objects near 
the zenith, or the pole, and similar to the one described by 
General Roy ; (see Philosophical Transactions, Vol. LXXX. 
p. 155) also a tube with a divided eye glass micrometer ; (see 
Philosophical Transactions, Vol. LXIX.) it has a power of 
80, but the images are not distinct, or equally bright, and 
the extent of the scale is so small, not more than jo', that it 
is, in truth, but of little use. The double eye tubes are com- 
posed of two eye glasses, to enlarge the field and render it 
more agreeable, both placed on the hither side of the cross 
wires, so that they may at any time be changed, without de- 
ranging the wires. The lowest of the compound eye tubes, 
with a power of about 6 o, is what is generally used for 
transits and polar distances.* For telescopical observations 

* If, as has been generally imagined, an angle of i' is about the smallest that is vi- 
sible to the naked eye, (Smith’s Optics, § 97) with a power of 60 times 1" will be- 
come visible; and, in that case, the power of this telescope will correspond with the le- 
vels, and the divisions, as was required above. 


10^ <SVr George Shuckburgh’s Account 

of the planets, higher powers may be put on ; and of these, 
that of 400 seems to be near the maximum that this glass will 
bear ; with 500 the image is not so well defined ; with 200 
or 300, it is beautifully distinct and bright ; but this inquiry 
demands more experiments than I have hitherto made, hav- 
ing been able to procure these high powers only within a few 
weeks. 

(23.) Having now given, as I apprehend, a very satisfac- 
tory idea of the accuracy of the parts of this instrument, I 
shall proceed to the method of adjusting them. This ma- 
chine, not being capable of having its polar axis laid horizon- 
tal, its adjustments, in some respects, will be different from 
those of small instruments of the same name. (See the me- 
thods proposed by Mr. Ramsden, in his Description, and by 
Mr. Vince, in his Practical Astronomy.) It may be proper 
to premise, that the principal points required are, 1st. to ad- 
just the level P, k, parallel to the declination axis U, V. 
2dly, to adjust this axis at right angles to the line of collima- 
tion of the telescope ; and, gdly, to make this axis at right 
angles to the polar axis. 

Probably others may be devised, but the inode I have 
adopted is as follows.* 

The polar axis is placed nearly in the meridian, by means 
of a meridian mark, previously verified, and elevated pretty 
nearly to the latitude of the place. This is to be done more 
accurately afterwards, by the sliding plates, and screws, at the 
bottom of the polar axis. 

* Whoever is desirous of seeing some very ingenious disquisitions of the errors and 
adjustment of this instrument, will do well to consult the Abbe Boscovich’s Opera 
pertinentia ad Astronomiam el Opticam, quarto, Bassani, 1785. Tomi 4ti Opuscu- 
lum i4tum. 


of the Equatorial Instrument. .105 

The axis of the declination circle is then brought nearly 
horizontal, by its proper level, viz. is turned round about the 
polar axis, till the bubble of the level stands true between the 
indexes ; the instrument is then turned half round about 
the polar axis, = 180°, shewn by the microscope W. If the 
bubble then stand true, it requires no correction, but if it do 
not, correct half the error, by moving the equatorial circle by 
its handle t, and the other half by the capstan screw a; (Tab. 
XIV. fig. 1) then turn the instrument back again to its first 
position, and see if the level stand true ; if not, repeat this 
operation till it does, correcting one half of the error by the 
equatorial handle, and the other half by the screw a. The 
declination axis will then be parallel to the level, and both of 
them to the horizon. It must be remarked, that in this ope* 
ration it will be necessary to move the declination circle 
round its own axis a little, in order to bring the same side of 
the level uppermost ; but this in no degree affects the result, 
for the imaginary line, round which this axis revolves, is what 
is meant all along by the axis, and is the line to which the 
parallelism of the level is referred. 

The declination axis remaining in an horizontal position, 
with the level above the axis, as in Tab. IX. turn the de- 
clination circle 180°, viz. till the level become below the 
axis ; then, by means of the pinion b, restore the tube of 
the level to an upright position, and see if the bubble stand 
true ; if not, correct \ the error by the screw c, and the 
•other \ by a. Now turn the declination circle 90° each 
way from its last situation, and repeat the examination of the 
bubble, and correct, as before, \ by the screw h , at right 
angles to c, and \ by the screw i; and if, after all these 

P 


MDCCXCIII, 


io 6 Sir George Shuckburgk’s Account 

corrections, in every part of an entire revolution gF the decli- 
nation circle round its axis, and of the level round its axis, the 
bubble stand true, it follows, that the axis of the declination 
circle, and of the level, are in every direction parallel to 
each other, both of them to the tangent of curvature in the 
middle of the level, and all three to the horizon. This ad- 
justment is therefore complete. 

(24.) It remains to be seen, whether the line of sight of 
the telescope is at right angles to the declination axis, and 
this latter to the polar axis. 

Take the error of the collimation of the telescope in right 
ascension, by a star in the equator, viz. let the transit of a star 
in the equator over the assumed meridian be observed, with 
the declination circle turned towards the east, and also to- 
wards the west. If there be any difference in these observa- 
tions, it will denote double the error of collimation in right as- 
cension, and half of it will be the deviation of the line of sight 
from a line at right angles to the axis of the declination circle ; 
and is correspondent to a similar adjustment of a transit instru- 
ment. The amount of this error being thus ascertained, let 
it be corrected by the screws, at the eye end of the telescope, 
that move the wires to the east and west. The declination 
axis, by means of its level, being restored to an horizontal 
position, let the centre wire of the telescope (by which is al- 
ways understood the line of collimation) be brought to bisect 
the meridian mark, by means of the sliding plate and adjust- 
ing screw below the polar axis, the telescope will then become 
a complete transit instrument ; for, by the first operation, the 
declination axis is made parallel to the level and its axis, and 
both to the horizon ; by the second, the line of sight is put 


of the Equatorial Instrument. toy 

at right angles to this axis ; and thirdly, it is adjusted to the 
meridian. 

Now, let the error of collimation in right ascension, in the 
same manner, be observed with any star out of the equator, by 
a circumpolar star, (the nearer the pole the better) suppose the 
pole star. If any difference should be noticed in its passage, 
with the circle east or west, halve that difference,* and it will 
be equal to the angle that the plane of the declination circle 
makes with the polar axis, if the observed star were actually 
in the pole ; if not, divide it by the sine of its declination, 
and the true angle of the plane of this circle (or of the line 
of collimation) with the polar axis, will be had. Again, if 
this operation be repeated with any other stars, and the error 
so found be divided by the sine of their declination, the error 
of the plane of the declination circle at the pole, viz. its 
greatest error, or angle with the polar axis, will be had. And 
note, if these observations are made with stars on each side 
of the equator, these quantities will be had in opposite direc- 
tions. Finally, the same may be done by two land objects, 
one to the north, and the other to the south ; the north and 
south meridian marks, for instance, proper consideration be- 
ing had to their declination ; by this means the error will be 
thrown in contrary senses, or doubled, and, from a variety of 
such results, a very correct mean quantity may ultimately be 

* By difference is here meant, the difference taken in minutes and seconds of a great 
circle passing through the star, and which can only be directly measured by a micro- 
meter ; but if, as is most convenient, this quantity should be observed by time, or by 
the divisions on the equatorial circle, (15 and 16) this quantity must be diminished in 
the proportion of the radius to the sine of the polar distance, viz. multiplied by the 
co-sine of the declination ; hence it is, that this method is capable of great preci- 

P 2 


sion. 


ioB Sir George Shuckburgh’s Account 

deduced ; and when found, must be corrected by the screws* 
at one end of the declination axis. I have been rather dif- 
fuse in the account of this adjustment, because it is one of the 
most important in the whole instrument, and does not readily 
present itself. 

It has now been seen that, ist, the level and its axis are 
parallel to the axis of the declination circle. 2dly, the line of 
sight at right angles to this axis, and parallel to the polar 
axis; and consequently the declination axis at right angles to 
the polar axis. 3dly, the polar axis parallel to that of the 
earth. These are the chief requisites in the adjustment of 
this instrument. Those that remain are secondary, and I 
shall take them in the following order, ist. The adjustment 
of the cross wires to the focus of the telescope. 2dly. The 
hanging level. 3dly. The line of collimation, north and 
south, as well as east and westward. 4thly. The index wires 
in the microscopes, ^thly. The refraction apparatus. And, 
6thly, the power and scale of the microscopes. 

(25.) First, the cross wires. Let the eye tube be adjusted 
to distinct vision for parallel rays by some distant object, such 
as Jupiter, Saturn, or Venus, by daylight; that done, ob- 
serve, while one limb of either of these planets appears run- 
ning along the equatorial wire, whether any motion of the 
eye, upwards or downwards before the eye glass, alters the re- 
lative place of the image and the wire ; if a motion of the 
eye upwards moves the planet in the same direction, the 
wires are too near the eye glass, and must be pushed in ; and 
vice versa , till the image become fixed upon the wire, what- 

* The heads of these screws being divided into 10 parts, and the value of each 
known, any given correction is easily applied. 


of the Equatorial Instrument. ice) 

ever be the motion of the eye. When this point is obtained, the 
eye stop with its wires, must be there fixed, for that is their 
true place; viz. the correct focal point of the object glass; 
and whatever indistinctness may be found, from the diver- 
sity of eyes of different observers, must be corrected by the 
motion of the eye glass only. Another point to be secured is 
the permanency, as far as may be, in the position of the ob- 
ject glass ; for if this be not correctly centered, which is very 
rarely the case, and indeed never to be expected, that is, if its 
axis be not concentric with the axis of the cell, in which it is 
fixed, any motion of this latter, by screwing or unscrewing it, 
may not only change the place of the focus, to which the 
wires are adjusted, but will necessarily move the line of col- 
limation, both in right ascension and declination.* To ob- 
viate this, therefore, two corresponding marks should be made, 
with a graver, both upon the cell, into which the glass is bur- 
nished, and also upon the tube of the telescope, into which 
the cell is screwed, or otherwise inserted, that in case the ob- 
ject glass should ever be taken out to clean it, &c. it may 
be restored very nearly, if not exactly, to its former po- 
sition. 

The eye glass, object glass, and wires, being thus settled 
in their respective places to each other, it will not be an im- 
proper time to measure the interval between the wires, which 
cannot be too accurately done, being of such constant use ; 
this may be either, ist, by observing the passage of a star in 
the equator, and making proper allowances for the rate of the 

* Bv moving my object glass an entire revolution in its screw, the line of collima- 
tion appears to move through a little circle of 50" in. diameter, so that the eccentricity, 
in this instance, appears to have been about T g 5 inch, 


no Sir George Shuckburgh's Account 

clock, or by a star out of the equator, and making proper al- 
lowance for the declination, in the proportion of the radius to 
the co-sine : or, edly, by means of the equatorial circle and a 
fixed land object ; and here the quantity must be diminis ed 
in the same ratio of the radius to the sine of the polar ins- 
tance. I have made use of both methods, as a confirmation 
of each other, and find the interval, which is equal in the 
three wires of my telescope, to be 7' 3 4/', 5 = 30", 3 sidereal 
time ; and these three wires divide the diameter of the field 
very nearly into four equal parts. 

(26.) Second and third adjustment ; the hanging level. By 
means of its proper handle u, move the declination circle 
about its axis, till the bubble of the hanging level /, m, rests 
true between the indexes, there fix it by the clamp w, re- 
verse the level, by taking it out of its pivots, and turning it 
end for end ; if the bubble now stand true, the level is ad- 
justed ; if not, correct \ the error by the declination handle, 
and the other \ by the small screw at the bottom of the level ; 
then reverse the level, and repeat this* operation till it does. 
The level, or rather a tangent to its curvature at its middle, 
will be parallel to the axis, on which it swings ; and both will 
be horizontal. At this time look through the telescope, and 
see what land object is covered by the horizontal wire ; now 
invert the telescope, by turning it 180° round the declination 
axis, and 180° round the polar, and bringing the level true, it 
will then point to nearly the same place ; and if exactly the 
same object as before be now covered by the horizontal wire, 
the axis of the level is adjusted parallel to the line of colli- 
mation, in a vertical direction ; if not, correct half the error 
by the little capstan screw at the bottom of the cock, or arm. 


of the Equatorial Instrument. n*r 

that supports one end of the axis of the level, and the other 
half by the declination handle ; invert the telescope, and re- 
peat the operation till the same object is covered in both po- 
sitions, and the level is found true ; then will the level and its 
axis be parallel to the line of collimation, and the object co- 
vered by the wire may be concluded to be in the horizon, 

(27.) Fourth. The index wires of the microscopes. The line: 
of collimation, with respect to east and west, has been already 
adjusted as above (sect. 24,) Let then the declination axis, by 
its level, be restored to an horizontal position; at this time adjust 
the index wires in the two equatorial microscopes W X, to bi- 
sect the two opposite divisions 360 and 180°, then will these- 
wires be rectified to their proper place. That being done, 
bring 90°, or the division that represents the equator on the^ 
declination circle, under its respective microscope, and turn 
the whole instrument one quarter round on the polar axis, 
viz. till 90° on the equatorial circle be bisected by the micro- 
meter ; and if, at this time, the bubble of the hanging level 
appear true, the index wire of the declination microscope is 
correct ; if not, correct half the error by the declination 
handle u, and half by the little screws b, (Tab. XI Y. fig. 2) at 
the side of the hanging level ; then reverse the telescope, viz. 
turn it till 270° on the equatorial circle come under the mi- 
crometer wire, and if the level then rest true, the adjustment 
is complete ; if not, repeat the operation, as before, till it 
does ; then, by its proper screw, bring the index wire of the 
declination micrometers to bisect the points 90 and 90°. The 
indexes of both circles will be then adjusted, and the axis of 
the hanging level brought parallel to the line of collimation, 
with respect to east and west, as ^well as with respect to 


ii3 Sir George Shuckburgh's Account 

north and south. Note, this parallelism of the axis of the 
level, to the line of collimation in a direction east and west, 
does not appear to be a very important rectification, but on 
some occasions may have its use. 

(28.) Fifth. The refraction piece. After what has been 
done, this apparatus will be easily adjusted. Bring the tele- 
scope, by means of its two levels P k, and / m, to point to the 
horizon, and in the meridian ; then, by the two pinions f, h, 
(Tab. X. fig. 3) of the refraction piece, bring its two levels e 
and g to rest true ; move the nonius d, of the little semicircle 
of the horary and vertical angles a, b, c, to the middle of the 
divisions, or o° o', and also that of the little quadrant of alti- 
tude /, k, to o° o', and this part is adjusted. 

(29.) Sixth. The microscopes. The magnifying power 
and scale of the microscopes is all that remains to be con- 
sidered. 

The magnifying power of a compound microscope, as is 
well known, (see Smith's Optics, § 127) depends on the pro- 
portion between the distance of the object, and of its image, 
from the object glass, together with the proportion between 
the focus of the eye glass, and ordinary focus of the eye, 
looking at a small object (suppose of ~ or inch). These 
two ratios compounded give the power of the microscope. 
The former is called magnifying by distance, and is a ma- 
terial part in the construction of these microscopes ; the scale 
of the micrometer being regulated by this part of the magni- 
fying power. For example, let the distance of the object from 
the glass be == 1, and the distance of its image = 4, its power 
will be 4 ; and consequently the scale of the micrometer, or 
motion of its screw, to ^answer to io', (suppose) must be 


ii3 


of the Equatorial Instrument. 

4 times as great as the space occupied by 10' on the limb of 
the circle ; and if the radius of the circle be 2 feet, an arc 
of io' will be equal to 0,07 inch nearly, on the limb ; and = 
0,28 inch on the scale, viz. = to the same arc on a circle of 
8 feet radius ; and if each revolution of the micrometer screw 
be intended to describe 1', the screw must contain about 35 
threads in an inch. But as it would be difficult to adjust the 
screw exactly to the scale, tile advantage of the construction 
of these micrometers is, the scale may at any time be ad- 
justed to the screw ; for let the interval between any two 
nearest divisions, — 10', on the limb, be measured by the screw, 
and suppose, instead of being = 10' or 600", it appears only 
= 570" ; it is evident, that the scale is bigger than it should 
be, or, which is the same thing, that the image is less by 
or In this case increase the distance between the 

micrometer wires, and the object glass, =~, by unscrewing 
or drawing out the tube, that carries the micrometer and eye 
glasses, and the scale is adjusted. It will at the same time, 
however, be necessary to re-adjust the object glass of the mi- 
croscope to distinct vision, by the screw of the cell, that con- 
tains it, until the image and the wires have no relative 
change of place by any motion of the eye. This will again 
occasion some small alteration in the scale, and must be cor- 
rected by repeated trials, and the scale adapted to the divi- 
sions on the arc ; and if the moveable wire of the microscope 
be now brought to coincide exactly with the fixed one, and 
the moveable index (with the mark ^.) brought to zero ( o ) 
on the screw head, the micrometer is completely adjusted. 
This having been done with all the microscopes, and the op- 
posite ones being made to agree, each with the other, in such 
MDCCXCIII, Q 


Sir George Shuckburgh’s Account 


ii 4 

manner, that the fixed wires may become a correct diameter, 
I believe the whole instrument will have been completely ad- 
justed. 

(30.) Before I conclude this account, I must beg leave to 
trouble the reader’s patience a few minutes more, in order to 
give a general idea of the manner of making the ordinary 
observations of right ascension and declination, with this in- 
strument. 

Let the telescope be adjusted towards the meridian mark, 
in such manner that the centre wire may exactly bisect it ; 
then note if the index wire of the equatorial micrometers 
bisect the points of 360° and 180°. ‘ If it does, the instru- 
ment is prepared for observing a transit ; if not, and the dif- 
ference be considerable, it must be corrected by moving the 
polar axis, by its adjusting screw. But as this quantity will 
seldom exceed 8" or 10", it will be more convenient to note 
this quantity in the journal, and allow for it afterwards in re- 
ducing the observations * As this quantity will from time to 

* This may be done by the following rule. 

_ . „ sine zenith dist. , , 

JE x sine r x — rr— = x the correction -f or — according as the tele- 

sine polar dist. 

scope points to the east or west of the meridian. 

Where JE is — the error on the equatorial circle. 

And P — the angle that the polar axis makes with a ray from the meridian mark. 

And if there should appear any error in the horizontal position of the axis of the 
declination circle at this time, by the level not standing true, that error may be cor- 
rected by this theorem. 

_ sine alt. , 

D X : 7 — x the correction. 

sine polar dist. 

Where D is — angle of depression of one end of this axis below the horizon. 

And by means of the above theorems, a table may be calculated that will give these 
corrections always, by inspection ; such a table I have computed for my own use, but 


of the Equatorial Instrument. 115 

time be variable, from a variety of causes, such as the pos- 
sible settling of the walls of the building; the partial or irre- 
gular expansion of the instrument, from the sun-beams acci- 
dentally falling upon it ; from the effect of a fire in the room, 
or the heat of a person's body in cold weather ; from the 
sun's heat upon the meridian mark, eastward in the morning, 
and westward in the afternoon ; from the same effect upon 
the observatory ; and lastly, possibly from a lateral refrac- 
tion of the ray coming from the meridian mark, from irregu- 
lar vapours floating near the surface of the earth. From 
some, or all of these causes, this quantity of error will be 
found to be exactly the same hardly for two days together ; 
but I have never yet known it to exceed 13" of a degree, = 
o",7 in time, during a period of more than a year, and very 
rarely above 6" or 7", sometimes on one side, and sometimes 
on the other. When this error is known, and set down, 
move the instrument about the polar axis by its handle t, till 
the divisions 360 and 180° are bisected by the equatorial 
wire ; this done, move the declination circle by its handle u, 
till the hanging level stands true ; and note the division on 
the declination circle cut by the micrometer wire, for 
that is the horizontal point, from whence the altitudes are 
to be reckoned. If the order of the divisions be such as to 
shew declinations, this division will be the angle of the co- 
altitude of the polar axis ; but if the divisions be such as in 
my instrument, it will be equal to the altitude of the polar 
axis, which should be equal to the latitude of the place. But 

as it is suited only to one latitude it is not given here. Tables, something similar to 
this, may be seen in Mr. Lud lam’s Astronomical Observations, Cambridge, 1769 ; 
and also in the Connoissance des Temps, pour 1792, p. 251. 


n6' Sir George Shuckburgh's Account 

as this will seldom happen, from the same reasons as have al- 
ready been mentioned, I prefer taking a memorandum of this 
quantity also, and allowing for it ; by which means I see its 
alteration, from time to time, compared with the weather, 
know better what I am about, than if I attempted to correct 
it, and save a great loss of time. From hence it must be 
seen that nothing is depended on, but that the instrument 
keeps its place during the four or five minutes that the ob- 
server is occupied in making the observation. 

(31.) The instrument is now prepared for an observation 
over the meridian, and also of the polar distance ; at which 
moment, if the weather should be cloudy, the observation in- 
complete, or unsatisfactory, it may be repeated as many 
times afterwards as is thought proper, taking notice of the 
distance from the meridian, shewn in the equatorial micro- 
scopes, and making allowance, in the reduction, for the mo- 
tion of the sun, or planet, during the interval ; for I esteem 
an observation made within 10 or 15 0 of the meridian, nearly 
equivalent to a meridian observation. But, if an observation 
should be made out of the meridian, the altitude and angle of 
the horary and vertical circles must be taken, by the refrac- 
tion apparatus ; and with these arguments, the refraction and 
parallax, in north polar distance, and in right ascension, may 
be found by inspection, in the tables that follow this account, 
and consequently every observation readily reduced to the 
meridian. 

(32.) 1 shall close this long history with an account of the 
probable accuracy of the observations made with this instru- 
ment, viz. of the amount of the probable errors, derived from 
an experience of more than twelve months. And first, with 


of the Equatorial Instrument. 117 

respect to those of right ascension. It must be readily seen, 
that the amount of these errors will be pretty nearly the 
same as those of any other transit instrument, whose magni- 
fying power, and length of axis, are the same. However, from 
actual trial, I lind that the passage of a star, near the equator, 
over any one wire in the field of the telescope, may be deter- 
mined to within | of a beat of the regulator, in strictness to 
about 3", 7, and, from a mean of the three wires, to within 
1 ",25 of a degree, = ~ of a second of time ; that is, if the 
wind be still, the weather favourable, and reasonable care be 
taken. And, from a series of observations of the sun's 
diameter throughout the year, it appears, the error in ordi- 
nary observations may be expected to lie within 3"; that it 
is 17 to 1 that this error does not amount to f', = ± of a se- 
cond of time ; and this includes some of the worst weather 
in which observations are likely to be made. I shall there- 
fore say, that 

The probability of error of an observation of a transit 
over the meridian, under tolerably favourable circumstances, 


from a mean of 3 wires, viz. in estimating the beat „ 
of the regulator, is about - - =2,0 

Add to this the error of setting the instrument to 
the meridian mark - - - = 1,0 

Add, also, the error in reading off the equatorial 
microscope - - - - = 0,5 


Total error of an observation in the meridian 
becomes - 

To this add the error of the divisions, and of the 
centre (at most) - 



= 1,0 


i iS Sir George Shuckburgh's Account 

Also the second reading off of the microscope - == 0,5 

And the total error of an observation of a transit out 
of the meridian, will be - - ■ - = 5,0 

The same, from actual experiment, in 13 trials, 
within 15 0 , on each side of the meridian (in Feb- 
ruary, 1792) - - - - - =7’5 

That is, that an observation made out of the meridian, will 
give the transit over the meridian true to { a second of 
time. 

The error in the observation of a polar distance may be put 
as follows. 

Error of the eye, in estimating the coincidence of 
the wire in the telescope with the object, the power ,, 


being 60 times - - - - = 1, 

Error of the divisions, and of the centre, in taking 
the horizontal point in the circle - - - = 1,- 

Error in reading this division off by the micro- 
scope - - - - = 0,5 

Error of the level, in ordinary observations - =2, 

Error of the divisions, and centre, a second time, 
viz. in taking the angle of the polar distance - =1, 

Error in reading off this division by the microscope = 0,5 


Sum of all these errors - - — 6,0 

Ditto, by actual observation of the line of collima- 
tion, the circle being turned east and west, from va- „ 
rious experiments, appears to be - - 7,5 

Lastly, if care be taken in the observation, and the 


H9 


of the Equatorial Instrument. 

sun not suffered to shine on the instrument, only 
during the moment of observation, I think no error 
in the polar distance need be apprehended exceeding 7, 

And in the meridian passage, none exceeding - 3,5 

So that it appears, that the right ascension will be observed 
with twice the precision of the polar distance. 

And here we must not omit to take notice, that of all the 
above mentioned causes of error, one only, viz. the error of 
the divisions in taking the polar distances, appears to be fixed, 
so that, by repeating the observation, the truth may be ap- 
proached to any given degree of accuracy. I have thought 
proper to make these remarks on the errors of the instru- 
ment, that if health and leisure should enable me hereafter to 
offer to the Royal Society the result of any astronomical ob- 
servations with it, it may be known to what claim to precision 
they are entitled. 

In describing the instrument, the following references in 
Tab. IX. were omitted in the text. 

ff> gg> bb 9 ii, are the eight conical radii to the declination 
circle, described page 78. 

11, 12, are two supporters to the clamp and endless screw, 
page 80. 

36, is a pair of steps, for the convenience of the observer. 


ISO' 


Sir George Shuckburgh's Account 


Explication and Use of the following Tables. 

The three first Tables are particularly calculated for the 
use of the large equatorial instrument, for the purpose of 
clearing observations with it from the effects of refraction 
and parallax. The four last are adapted more peculiarly to 
the small or portable equatorial, such as has been noticed in 
sect. 10, and which I thought might be acceptable to such 
persons as have the good fortune to possess one of these in- 
struments. Of these I ables in their order. 

Table I. gives the correction of the refraction in north po- 
lar distance, by entering it with the altitude at the top, and the 
angle of the horary and vertical circles on the left hand side ; 
and in the common point of meeting is found a quantity, in 
seconds and decimals, that is to be added to the apparent po- 
lar distance, to give the true ; this correction is always addi- 
tive. But if the same table be entered with the angle of the 
horary and vertical circles, in the right hand column, it will 
give the refraction in right ascension, by multiplying the 
quantity here found by the secant of the declination, to be 
found in Table IV. 

Table II. gives the effect of the sun’s parallax in right as- 
cension and north polar distance, and is to be entered with 
the same arguments as Table I. ; and the parallax in right 
ascension is to be multiplied by the secant of the declination, 
as before; the sun’s horizontal parallax being assumed = 8 ", 6 . 

Table III. is a similar Table, only calculated to an hori- 
zontal parallax of 10" : so that whatever be the parallax of 
the sun or planets, this correction may readily be found, al- 
most by inspection. 


of the Equatorial Instrument. 


Table IV. is the natural secants to each degree, extracted 
from Sherwin's Tables ; being of such constant use in these 
computations, I have placed it with these tables of refraction. 

Table V. gives the correction of the time; viz. of the sun or 
star's distance from the meridian, in an observation with a 
portable equatorial, not previously adjusted to the meridian ; 
this quantity is to be multiplied also by the secant of the 
declination. 

Table VI. as its title imports, gives the correction of the 
meridian line in minutes and decimals, which was thought 
near enough for a portable instrument ; the quantity here 
found is to be multiplied by the secant of the altitude. 

Table VII. similar to Table I. only reduced to seconds of 
time, gives the refraction in right ascension, suited to the usual 
mode of dividing the small instrument ; viz. into civil hours 
and minutes. 

Table VIII. similar also to Table I. gives the refraction in 
declination. The arguments are the same in all the Tables ; 
viz. the altitude, and the angle of the horary and vertical circles ; 
which appeared to me the only means of making the Tables 
universal, and adapted to all latitudes.* 

Their foundation is this : 


* A table of refraction in right ascension and declination, for the latitude of Paris 
cnly, may be met with in the Connoissance des Temps, pour 1791. What I have given 
in the following account, viz. Tab. V. VI. VII. and VIII. I calculated for my own use, 
as early as the year 1774. 


Let AB be a portion of a 
vertical circle = the refraction 
in altitude ; DA a parallel to 
the horizon ; and D B a paral- 



MDCCXCIII. 


R 


122 Sir George Shuckburgh's Account 

lei to the equator : then A C will be a portion of an horary 
circle = the refraction in declination, found by Table I. and 
Table VIII. z. CAB, the angle of the horary and vertical 
circle ; CB, the refraction in right ascension, found by Table 
I. and Table VII. DA, the correction of the meridian, found 
by Table VI. ; and DB, the correction of the time, found by 
Table V. ; and, as AB will hardly ever be found to exceed 30', 
these triangles have been considered all as plane ; making 
due allowance, in the proportion of the sine to the radius, for 
the distances of the arcs DA, BC, and DB from their respec- 
tive poles, which has been noticed at the foot of each Table * 
The refraction in altitude having been taken from Professor 
Mayer's Tables, London edition, 1770, which is calculated 
for a density of the air, expressed by 2 9,6 inches of the ba- 
rometer, and 50°of Fahrenheit's thermometer; and, for any 
other heights of the barometer and thermometer, may be 
corrected in the usual way ; making an allowance for each de- 
gree of Fahrenheit's thermometer, above or below 50°, of 
XT9C5- This correction has been deduced from the result of 
a great many observations that I made some years since with 
the manometer, described in the Philosophical Transactions 
for the year 1777, Vol. LXVII. p. 564,. The equation that 
astronomers have generally been used to adopt, from Dr. 
Bradley's Observations, is for each degree of the ther- 
mometer ; but, I think, erroneously. 

* 1 have proposed multiplying by the secant, instead of dividing by the co-sine, as 
being the readier operation, and which comes to the same thing. 


£ To face p . 122 . 

No I. Table of the Effect of Refraction in North Polar Distance. 

This correction is always -f . 


Angle of 
the verti- 
cal with 








DEGREES 

OF ALTITUDE. 











Angle of 
the verti- 
cal with 
the 

horary 


























horary 

circle. 

2° 


4 ° 

6° 

8° 

IO° 

12° 

1 4 ° 


1 6° 

1 8° 

20° 

22° 


n aO 

24 

26° 

28° 

O 

O 

CO 

circle. 


/ // 

/ 

// 

t 

11 

/ II 

/ // 

/ ft 

/ // 

r 

// 

/ 

11 

/ 

II 

/ 

11 

/ 

11 

/ 

II 

/ 

II 

/ 

II 


O 

18 1 

1 1 

4 2 

8 

25 

6 30 

5 i 5 > 6 

4 24,0 

3 4 6 >4 

3 

17-5 

2 

54-7 

2 

36-3 

2 

20,9 

2 

8,0 

1 

57 > z 

1 

47-6 

1 

39 -o 

90 

2 

l8 O 

1 1 

42 

8 

24 

6 30 

5 i 5*3 

4 23,8 

3 46-3 

3 

17-4 

2 

54-6 

2 

36,2 

2 

20,8 

2 

7-9 

1 

57 -i 

1 

47-5 

I 

38,9 

88 

4 

I 7 58 

1 1 

40 

8 

24 

6 29 

5 J 4'7 

4 23.4 

3 45-9 

3 

17.0 

2 

54-3 

2 

35-9 

2 

20,6 

2 

7-7 

1 

56,9 

1 

47-3 

I 

38,8 

86 

6 

‘7 55 

1 1 

37 

8 

22 

6 28 

5 1 3-»8 

4 22,5 

3 45-2 

3 

16,4 

2 

53-7 

2 

35-4 

2 

20,1 

2 

7-3 

1 

56,6 

1 

47 -o 

I 

38,5 

84 

8 

17 50 

1 1 

35 

8 

20 

6 26 

5 12,6 

4 21,4 

3 44-2 

3 i 5 > 6 

2 

53 =° 

2 

34-8 

2 

19-5 

2 

6,8 

1 

56,1 

1 

46,6 

I 

38,0 

82 

10 

17 44 

1 1 

3 i 

8 

17 

6 24 

5 10,8 

4 20,0 

3 43-0 

3 

14-5 

2 

52,0 

2 

33-9 

2 

18,8 

2 

6,1 

1 

55-4 

1 

46,0 

I 

37-5 

80 

12 

17 37 

1 1 

27 

8 

H 

6 21 

5 8,7 

4 18,2 

3 4 i -4 

3 

12,8 

2 

5°, 9 

2 

32-9 

2 

17,8 

2 

5-2 

1 

54-6 

1 

45-2 

I 

36,8 

78 ' 

14 

17 29 

1 1 

21 

8 

IO 

6 18 

5 6,3 

4 16,2 

3 39-7 

3 

1 1,6 

2 

49-5 

2 

3 i -7 

2 

16,7 

2 

4,2 

1 

53-7 

1 

44-4 

I 

36,1 

76 

16 

17 19 

1 1 

15 

8 

5 

6 15 

5 3-3 

4 13-7 

3 37-6 

3 

9,8 

2 

47-9 

2 

30,2 

2 

15-4 

2 

3 -o 

1 

52,7 

1 

43-4 

I 

35-2 

74 

“18 

17 8 

1 1 

7 

8 

0 

6 1 1 

5 °-3 

4 11, 1 

3 35-3 

3 

7-8 

2 

46,1 

2 

28,7 

2 

14,0 

2 

i -7 

1 

5 i -5 

1 

42-3 

I 

34 >i 

72 

20 

16 56 

1 1 

0 

7 

54 

6 7 

4 5 6 -7 

4 8,i 

3 32-8 

3 

5 - 6 

2 

44 -i 

2 

26,9 

2 

12,4 

2 

o -3 

1 

50,1 

1 

41-1 

I 

33 -o 

70 

22 

16 41 

10 

5 i 

7 4 ° 

6 1 

4 53 

4 4-8 

3 29,9 

3 

3-2 

2 

42.0 

2 

24-9 

2 

10,6 

1 

58,7 

1 

48-7 

1 

39-7 

I 

3 1 >8 

68 

24 

16 28 

10 

4 i 

7 

41 

5 5 6 

4 48 

4 1-2 

3 26,9 

3 

°-5 

2 

39-6 

2 

22,8 

2 

8-7 

1 

56,9 

1 

47-1 

1 

38.3 

I 

3°>4 

66 

26 

16 12 

10 

3 i 

7 

34 

5 5 ° 

4 44 

3 57-3 

3 23,5 

2 

57-6 

2 

37 -o 

2 

20,5 

2 

6,6 

1 

55 -o 

1 

45-4 

1 

36,7 

I 

29,0 

64 

28 

15 55 

10 

20 

7 

26 

5 44 

4 39 

3 53 -i 

3 20,0 

2 

54-5 

2 

34-2 

2 

1 8,0 

2 

4-4 

1 

53 -o 

1 

43-5 

1 

35-8 

I 

27.4 

62 

” 3 ° 

15 3 6 

IO 

8 

7 

*7 

5 38 

4 33 

3 48,6 

3 16,1 

2 

5 i-i 

2 

3 i -3 

2 

15.1 

2 

2,0 

1 

50,8 

1 

4 i -5 

1 

33 -i 

I 

25-7 

60 

32 

15 17 

9 

55 

7 

8 

5 31 

4 28 

3 43-9 

3 12,0 

2 

47-6 

2 

28,1 

2 

1 2,6 

1 

59-5 

1 

48-5 

1 

39-4 

1 

31,2 

I 

24,0 

58 

34 

14 56 

9 

42 

6 

58 

5 23 

4 22 

3 38,9 

3 7-8 

2 

43-8 

2 

24,8 

2 

9.6 

I 

56,8 

1 

46,1 

1 

37-2 

1 

29,1 

1 

22,1 

56 

3 6 

•4 34 

9 

28 

6 

48 

5 16 

4 15 

3 33-6 

3 3-2 

2 

39.9 

2 

21,3 

2 

6-5 

1 

54 -o 

1 

43-6 

1 

34-9 

1 

27,0 

1 

20,1 

54 

38 

14 12 

9 

*3 

6 

38 

5 7 

4 9 

3 28,0 

2 58,4 

2 

35-6 

2 

17,6 

2 

3 > 2 

1 

51,0 

1 

40,9 

1 

32-4 

1 

24,7 

I 

18,0 

52 

40 

13 48 

8 

58 

6 

27 

4 59 

4 2 

3 22,2 

2 53-4 

2 

31-3 

2 

1 . 3-7 

I 

59-8 

1 

47-9 

1 

38,0 

1 

29,8 

1 

22,3 

I 

15,8 

5 ° 

42 

13 23 

8 

4 i 

6 

l S 

4 5 ° 

3 55 

3 16,1 

2 48,2 

2 

26,7 

2 

9-7 

I 

56,1 

1 

44-7 

1 

35-1 

1 

27,1 

1 

1 9-9 

I 

13-5 

48 

44 

12 58 

8 

2 5 

5 

3 

4 4 ° 

3 47 

3 9-9 

2 42,9 

2 

22,1 

2 

5-6 

I 

52.4 

1 

4 i -4 

1 

32,1 

t 

24,4 

1 

17.4 

I 

1 1,2 

46 

46 

12 31 

8 

7 

5 

5 i 

4 3 i 

3 39 

3 3-4 

2 37-3 

2 

17-1 

2 

i -4 

I 

48,6 

1 

37-9 

1 

28,9 

1 

21,5 

1 

14-7 

I 

8,8 

44 

48 

12 3 

7 

49 

5 

38 

4 21 

3 3 i 

2 56,6 

2 3 i -5 

2 

12,1 

1 

56,9 

1 

44,6 

1 

34-3 

1 

25,6 

1 

18,5 

1 

12,0 

I 

6,2 

42 

5 ° 

11 35 

7 

3 i 

5 

2 4 

4 11 

3 23 

2 49-7 

2 25,6 

2 

6,9 

1 

5 2 -3 

I 

40,5 

1 

30,6 

1 

22,3 

1 

15-4 

1 

9 >i 

I 

3-6 

40 

!>2 

1 1 6 

7 

12 

5 

1 1 

4 0 

3 H 

2 42.5 

2 i 9-3 

2 

1,6 

1 

47-5 

I 

36 6 

I 

26,8 

1 

18,8 

1 

12,2 

I 

6,2 

I 

1-0 

38 

54 

10 35 

6 

5 2 

4 

57 

3 49 

3 6 

2 35-2 

2 13-8 

I 

56,6 

1 

42-7 

1 

3 1 . 9 

1 

22,9 

1 

15,2 

1 

9,0 

1 

3-2 


58,2 

36 

5 6 

10 4 

6 

33 

4 

42 

3 38 

2 57 

2 27,6 

2 6,6 

1 

5°>5 

1 

37-7 

I 

27-4 

1 

18,8 

1 

1 1,6 

1 

5-6 

1 

0,1 


55-4 

34 

58 

9 33 

6 

12 

4 

27 

3 27 

2 47 

2 19,9 

2 0,0 

1 

447 

1 

32,6 

I 

22,9 

1 

14.7 

1 

7-8 

1 

2,2 


57 -o 


52,5 

3 2 

60 

9 0 

5 

5 i 

4 

12 

3 15 

2 38 

2 12,0 

1 53-2 

1 

387 

1 

27.3 

I 

18,1 

1 

10,4 

1 

4.0 


58,6 


53-8 


49-5 

3 ° 

62 

8 27 

5 

3 ° 

3 

57 

3 3 

2 28 

2 3-9 

1 46.3 

1 

32-7 

1 

22,2 

I 

13-3 

1 

6,2 

1 

0,1 


55 -o 


50-5 


46,5 

28 

64 

7 54 

5 

8 

3 

4 1 ■ 

2 51 

2 18 

1 55-7 

1 39-3 

1 

26,6 

1 

16,6 

I 

8-5 

1 

1,8 


56,1 


5 i -4 


47 -i 


43-4 

26 

66 

7 19 

4 4 6 

3 

25 

2 39 

2 8 

1 47-4 

1 32,1 

1 

20,3 

1 

1 1, 1 

1 

3-5 


57-3 


52,1 

t 

47-7 


43-7 


40-3 

24 

68 

6 45 

4 

23 

3 

9 

2 26 

1 58 

1 38.9 

1 24,9 

1 

14,0 

1 

5-5 


58,5 


52,8 


47-9 


43-9 


40.3 


37 -i 

22 

70 

6 10 

4 

O 

2 

52 

2 13 

1 48 

1 3°-3 

1 17-5 

1 

7-6 


59-8 


53-5 


48,2 


43-8 


40,1 


36,7 


33-9 

20 

72 

5 34 

3 

37 

2 

36 

2 1 

1 37 

1 21,6 

1 9-9 

1 

1-1 


54 -o 


48-3 


43-6 


39-6 


36-3 


33-2 


30,6 

18 

74 

4 58 

3 

13 

2 

‘9 

1 47 

1 27 

1 12,8 

1 2,4 


54-5 


48,1 


43 -i 


38.9 


35-3 


32,6 


29,6 


27-3 

16 

76 

4 22 

2 

5 ° 

2 

2 

1 34 

1 16 

1 3-9 

0 54,8 


47-8 


42,1 


37-8 


34 - 1 


31,0 


28,4 


26,0 


24,0 

14 _ 

7 « 

3 45 

2 

26 

1 

45 

1 21 

1 5 

0 54,9 

47 -i 


41,1 


36,1 


32-5 


29-3 


26,6 


24-3 


22,4 


20,6 

12 

80 

3 8 

2 

2 

1 

27 

1 7 

0 55 

45-8 

39-3 


34-3 


30.2 


27,1 


24,4 


22,2 


20,3 


18,6 


17,2 

10 

82 

2 30 

1 

38 

1 

10 

0 54 

0 44 

3 6 -7 

31,6 


2 7-5 


24-3 


21,7 


19,6 


17-8 


16,3 


H -9 


1 3-8 

8 

84 

* 53 

1 

‘3 

0 

53 

0 41 

0 33 

27,6 

23.5 


20,7 


18,4 


16,3 


14-7 


13-4 


12,2 


1 1,4 


10,3 

6 

86 

* 15 

0 

49 

0 

35 

0 27 

0 22 

18,4 

15,8 


13-7 


12,3 


10,9 


9-8 


8,9 


8,2 


7-5 


6,9 

4 

88 

0 38 

0 

2 5 

0 

17 

0 13 

0 11 

9-3 

7-9 


6,9 


6,2 


5-5 


4-9 


4-5 


4.1 


3-8 


3-5 

2 

90 

0 0 

0 

0 

0 

0 

0 0 

0 0 

0 0,0 

0 0,0 

0 

0,0 

0 

0,0 

O 

0,0 

0 

0,0 

0 

0,0 

.0 

0,0 

0 

0,0 

0 

0,0 

0 


Refraction in right ascension, x sec 1 declination. 

This correction is — on the east, and -f on the west side of the meridian. 



[^Toface p. 122. 


No I. Table of the Effect of Refraction in North Polar Distance, continued. 


This correction is always -f . 


Angle of 
the verti- 
cal with 
the 










DEGREES 

OF ALTITUDE. 






Angle of 
the verti- 
cal with 
the 

horary 




















horary 

circle. 


3 2° 


34 ° 


36° 


38° 

0 

0 

A O® 

42 

44 ° 

46 ° 

48° 

5 °° 

52 0 

54 ° 

56° 

58° 

6o° 

circle. 

O 


// 

, 

// 


// 


// 

/ // 

/ " . 

// 

// 

H 

// 

// 

// 

// 

// 

// 

O 

O 

X 

3 i -5 

1 

24-7 

1 

18,7 

1 

13,2 

1 8,2 

i 3-6 

59-3 

55-3 

51,6 

48,1 

44-9 

4 i -7 

38-7 

35-8 

33 -i 

90 

2 

1 

3^4 

1 

24,6 

1 

18,7 

1 

13,2 

1 8,2 

1 3,6 

59-3 

55-3 

51,6 

48,1 

44-9 

41.7 

38,7 

35-8 

33 -i 

88 

4 

1 

3 1 '3 

1 

24.5 

1 

18,5 

1 

13,2 

1 8,0 

1 3-4 

59-2 

55-2 

5 i -5 

48,0 

44-8 

41,6 

38-6 

35-7 

33 -o 

86 

6 

1 

3 1 ’ 0 

1 

24,2 

I 

18,3 

1 

12,8 

1 7,8 

1 3-3 

59 -° 

55,0 

5 i -3 

47-8 

44-7 

4 i -5 

38,5 

35-6 

32,9 

84 

8 

1 

30,6 

1 

23-9 

1 

17-9 

1 

12,5 

1 7-5 

1 3,0 

58.7 

54-8 

5 i-i 

47-6 

44-5 

4 i .3 

38-3 

35-5 

32,8 

82 

10 

1 

3 °, 1 

1 

2 3>4 

1 

17-5 

1 

12,1 

1 7,2 

1 2,6 

58-4 

54-5 

50,8 

47-4 

44-2 

41,1 

38,1 

35-3 

32,6 

80 

12 

1 

2 9’5 

1 

22,8 

1 

17.0 

1 

1 1,6 

1 6,7 

i 2,2 

58,0 

54 -i 

50.5 

47-0 

43-9 

40,8 

37-8 

35 -o 

32,4 

78 

14 

1 

28,8 

L 

22,2 

1 

16,4 

1 

1 1,0 

1 6,2 

1 i -7 

57-5 

53-7 

50,1 

46,7 

43-6 

40,5 

37-5 

34-7 

32,1 

76 

16 

I 

28,0 

I 

21-4 

1 

15,6 

1 

10,4 

X 5,6 

1 1,2 

57 -o 

53-2 

49-6 

46,2 

43-2 

40,1 

37-2 

34-4 

31-8 

74 

18 

1 

27,0 

X 

20,5 

1 

14,8' 

1 

9.6 

1 4-9 

1 0,5 

56,4 

52,6 

49 >i 

45-7 

42-7 

39-6 

36,8 

34 >o 

3 i ,5 

72 

20 

1 

26,0 

I 

19-7 

1 

13-9 

1 

8,8 

1 4,1 

59-8 

55-7 

52,0 

48-5 

45-2 

42,2 

39-2 

36-3 

33-6 

3 i.i 

70 

22 

1 

24,9 

I 

18,5 

1 

12,9 

1 

7-9 

1 3 > 2 

59 -° 

55-0 

5'»3 

47-9 

44-6 

41,6 

38,6 

35-9 

33-2 

30,7 

68 

24 

1 

23,6 

I 

17-4 

1 

1 1,9 

1 

6,9 

1 2,3 

58,2 

54-2 

50,5 

47-1 

43-9 

41,0 

38,1 

35-3 

32,7 

30,2 

66 

26 

1 

22,3 

I 

16,1 

1 

10,7 

1 

5-8 

1 i -3 

57-2 

53-3 

49-7 

46-4 

43-2 

40-3 

37-4 

34-8 

32,2 

29,8 

64 

28 

1 

20,9 

I 

14,8 

1 

9-5 

1 

4-7 

1 0,2 

56,2 

52.4 

48,9 

45-6 

42.5 

39-6 

36,8 

34-2 

31,6 

29,2 

62 

3 ° 

1 

> 9-3 

I 

1 3-3 

1 

8,1 

1 

3-4 

59 -i 

55-2 

51.4 

47-9 

44,8 

41,6 

38-9 

36,1 

33-5 

3 J -o 

28,7 

60 

3 2 

1 

17.7 

I 

ii -7 

1 

6,7 

1 

2,1 

57-9 

54.0 

50-3 

46-9 

43-8 

40,8 

38 ,x 

35-3 

32,8 

30.3 

28,1 

58 

34 

1 

15,8 

I 

10,2 

1 

5,2 

1 

0,7 

56,6 

52,7 

49,2 

45-9 

42,8 

39-9 

37-2 

34-5 

32,0 

29.6 

27-5 

56 

3 6 

1 

14,0 

I 

8-5 

1 

3-6 


59-3 

55-2 

5'-5 

48,0 

44-8 

41,8 

38,9 

36,3 

33-7 

31-3 

28,9 

26,8 

54 

38 

1 

12,1 

I 

6-7 

1 

i -9 


57-7 

53-8 

50,1 

46,8 

43-6 

40-7 

37-9 

35-4 

32,8 

30-4 

28,2 

26,1 

52 

4 ° 

1 

10,1 

I 

4,8 

1 

0,2 


56,1 

52,3 

48,8 

45-5 

42,4 

39-6 

36,9 

34 - 4 * 

3 i >9 

29,6 

27-4 

25,4 

5 ° 

4 2 

1 

8,0 

I 

2,8 


58,4 


54-4 

5°>7 

47-3 

44 -i 

41,2 

38-4 

35-8 

33-3 

3°>9 

28,7 

26,5 

24,6 

48 

44 

1 

5>9 

I 

0,8 


56,5 


52-7 

49 -i 

45-8 

42.7 

39-9 

37-2 

34,6 

32,3 

2 9-9 

27,8 

25,7 

23,8 

46 

46 

1 

3 ’4 


58,7 


54-6 


5°- 9 

47-4 

44-2 

4 i -3 

38,5 

35-8 

33-4 

31-2 

28,9 

26,8 

24,8 

23,0 

44 

48 

1 

1, 1 


50,7 


52,7 


49 >° 

45-7 

42-5 

39-8 

37 -o 

34-5 

32,2 

30.0 

27,8 

25.9 

23-9 

22,2 

42 

5 ° 


5 8,8 


54-4 


50,6 


47 -i 

43-9 

40,9 

37-8 

35-5 

33-2 

30,9 

28,8 

26,8 

24-9 

22,9 

21,3 

4 ° 

5 2 


5 6 -3 


52,1 


48.4 


45,1 

42,1 

39-2 

36,5 

34-1 

31-8 

2 9-7 

27,6 

25-7 

23,8 

22,0 

30,4 

38 

54 


53-8 


49-7 


46,2 


43 -i 

40,2 

37-4 

34-9 

32,5 

30-4 

28,3 

26,4 

24-5 

22,7 

21,0 

19-5 

36 

56 


51,2 


47-3 


44,0 


41,0 

38,2 

35-6 

33-2 

31-0 

28,9 

26,9 

25,1 

23-3 

21,6 

1 9-9 

18,6 

34 

58 


48,4 


44-9 


41.7 


38-9 

36,2 

33-7 

3 i .5 

29,4 

27,4 

25-5 

23,8 

22,1 

20,5 

18,9 

17,6 

32 

60 


45-8 


42-3 


39-3 


36,6 

34 -i 

31-8 

29,6 

27,6 

25,8 

24,0 

22,5 

20,8 

19-3 

' 7-9 

16,5 

30 

62 


42,9 


39-7 


3 6 -9 


34-4 

32,1 

29.9 

27-9 

26,0 

24,2 

22,5 

21,1 

19,5 

18,1 

1 6,8 

1 5-5 

28 

64 


40,1 


37-1 


34-4 


32,1 

3 °-i 

2 7-9 

26,1 

2 4>3 

22,7 

2 1 ,0 

19-7 

1 8,2 

16,9 

15-7 

i 4-5 

26 

66 


37 - 2 


34-4 


3 i -9 


29,8 

27,8 

25,9 

24,2 

22,6 

21,0 

19-5 

18,3 

16,9 

15-7 

14,5 

i 3-4 

24 

68 


34-3 


31,6 


29,4 


27.4 

25,6 

23,8 

22,2 

20,8 

19-4 

18,0 

16,9 

15-5 

14,4 

13-4 

12,4 

22 

, 70 


3 i »3 


29,0 


26,9 


25, X 

23.4 

2 1 ,7 

20,4 

18,9 

1 7,6 

16,4 

15-4 

i 4-3 

13-2 

1 2,2 

1 r -3 

20 

7 2 


28,3 


26,2 


24-3 


22,7 

21,1 

19.7 

18,3 

17-1 

16,0 

14,8 

13-9 

1 2,9 

1 2,0 

1 1,0 

10,2 

18 

74 


2 5>3 


23 3 


21,7 


20,2 

18,8 

1 7-6 

16,4 

15-3 

H ,3 

13,2 

12,4 

11,5 

10,6 

9,8 

9 -i 

16 

76 


22 2 


20,5 


19,0 


17,8 

16,6 

15-4 

14-4 

13-4 

12,5 

1 1 ,6 

10,9 

10,1 

9-3 

8,6 

8,0 

14 

78 


19,0 


17,6 


16,3 


15-3 

14,2 

13-2 

12,4 

ii -5 

10,8 

10,0 

9-4 

8,6 

8,0 

7-4 

6,9 

1 2 

80 


15-9 


14,6 


13,6 


12,8 

1 1,9 

x 1,0 

10,3 

9,6 

8,9 

8,3 

7-8 

7-2 

6-7 

6,1 

5-7 

10 

82 


12,8 


ii >7 


10,9 


10,3 

9,6 

8,9 

8-3 

7-8 

7-2 

6.7 

6-3 

5-7 

5-4 

5 -o 

4 - 6 

8 

84 


9,6 


8,8 


8,2 


7-7 

7-2 

6-7 

6-3 

5-8 

5-4 

5 -o 

4-7 

4-4 

4,0 

3-8 

3-4 

6 

86 


6,5 


5-8 


5-4 


5-2 

4-8 

4-5 

4,2 

3-9 

3-7 

3-4 

3 -i 

2,9 

2,6 

2-5 

2-3 

4 

88 


3 - 2 


2,9 


2,7 


2,6 

2,4 

2-3 

2,1 

2,0 

i -9 

i -7 

1,6 

i -5 

1-4 

i -3 

1,2 

2 

90 

0 

0,0 

O 

0,0 

0 

0,0 

0 

0,0 

0 0,0 

0 0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0 


Refraction in right ascension, x sec' declination. 

This correction is — on the east, and -f- on the west side of the meridian. 

And is to be applied to the sun or star’s distance from the meridian, observed on the equatorial circle. 








I 


XTojacep. 122. 


No HI- Table of the Effect of Refraction in North Polar Distance, continued. 

This correction is always -f . 


Angle of 
the verti- 
cal with 


DEGREES OF ALTITUDE. 


Refraction in right ascension, x sec 1 declination. 

This correction is — on the east, and + on the west side of the meridian. 


horary 

circle. 

62° 

H 

3°>5 

3°>5 

3°-4 

64° 

II 

28,0 
28,0 
2 7,9 

66° 

// 

2 5-5 

25,5 

25,4 

68° 

II 

23,2 

23,2 

23,1 

70° 

n 

20,9 

20,9 

20,8 

7 2 

a 

18,7 

18,7 

18,7 

74 ° 

II 

16,5 

16,5 

16,5 

76° 

// 

* 4-4 

14,4 

14,4 

78° 

II 

12,3 

12,3 

*2,3 

8o° 

n 

10,2 

10,2 

10,2 

82° 

II 

8.1 

5.1 

8.1 

84° 

n 

6,1 

6,1 

6,1 

86° 

a 

4,0 

4,0 

4,0 

88° 

a 

2,0 

2,0 

2,0 

90° 

U 

0,0 

horary 

circle. 

0 

O 

2 

4 

O 

90 

88 

86 

6 

3°-3 

27,8 

25,4 

23,1 

20,8 

18,6 

16,4 

* 4-3 

12,2 

10,1 

8,1 

6,1 

4,0 

2,0 


84 

8 

30,2 

2 7-7 

25,2 

23,0 

20 ,7 

18,5 

16,3 

H -3 

12,2 

10,1 

8,0 

6,0 

4,0 

2,0 


82 

10 

30.0 

27,6 

25,1 

22,8 

20,6 

18,4 

16,2 

14,2 

1 2,1 

10,0 

8,0 

6,0 

3-9 

2,0 


80 

12 

29,8 

27,4 

24,9 

22,7 

20,4 

18,3 

16,1 

14,1 

12,0 

10,0 

7-9 

6,0 

3-9 

2,0 


78 

H 

29,6 

27,2 

24,7 

22,5 

20,3 

18,1 

16,0 

14,0 

1 1,9 

9,9 

7-9 

5-9 

3-9 

i -9 


76 

16 

29,3 

26,9 

24,5 

22.3 

20,1 

1 8,0 

15,9 

13,8 

11,8 

9,8 

7-8 

5-9 

3-8 

1.9 


74 

x8 

29,0 

26,6 

24,2 

22,1 

19-9 

17,8 

l 5>7 

* 3-7 

n ,7 

9,7 

7,6 

5-8 

3-8 

1-9 


72 

20 

28,7 

26,3 

24,0 

21,8 

19,6 

17,6 

* 5-5 

13,5 

1 1,6 

9,6 

7-6 

5-7 

3-8 

1-9 


70 

22 

28,3 

26,0 

23,6 

21,5 

19-4 

17,3 

1 5 »3 

i 3,3 

11,4 

9-5 

7,5 

5-7 

3-7 

1,8 


68 

24 

27,8 

25,6 

2 3-3 

21,2 

19,0 

J 7 ,i 

15,1 

* 3 ,* 

1 1,2 

9-3 

7-4 

5-6 

3,6, 

1,8 


66 

26 

2 7-4 

25,2 

22,9 

20,8 

18,8 

16,8 

14,8 

12,9 

1 1,1 

9,2 

7-3 

5-5 

3-6 

1,8 


64 

28 

26,9 

24,7 

22,5 

20,5 

18,4 

16,5 

14,6 

12,7 

10,9 

9,0 

7 -i 

5-4 

3-5 

1,8 


62 

30 

26,4 

24,2 

22,1 

20,1 

18, i 

16,2 

J 4>3 

12,5 

xo,6 

8,8 

7 »° 

5-3 

3-5 

1,7 


60 

32 

25,8 

2 3-7 

21,6 

19,7 

» 7-7 

I 5»9 ' 

14,° 

12,2 

10,4 

8,6 

6,9 

5-2 

3-4 

1,7 


58 

34 

25.3 

23.2 

21,1 

19,2 

J 7-3 

* 5-5 

! 3>7 

11,9 

10,2 

8-5 

6,7 

5 -i 

3-3 

1-7 


56 

3 6 

24,7 

22,6 

20,6 

18,8 

16,9 

15,1 

* 3,3 

1 1,6 

9,9 

8,2 

6,5 

4-9 

3-2 

1,6 


54 

38 

24,0 

22,1 

20,1 

18,3 

16,5 

14,7 

13,0 

1 *>3 

9,7 

8,0 

6,4 

4,8 

3 -i 

1,6 


52 

40 

23.4 

21,4 

19,5 

17,8 

16,0 

H ,3 

12,6 

1 1,0 

9,4 

7-8 

6,2 

4-7 

3 >i 

i -5 


50 

42 

22,7 

20,8 

18,9 

17,2 

* 5^5 

13,9 

12,3 

10,7 

9 >* 

7,6 

6,0 

4-5 

3 >o 

i -5 


48 

44 

22,0 

20,1 

18,3 

16,7 

15,0 

1 3-4 

1 1,9 

10,4 

8,8 

7-3 

5-8 

4-4 

2-9 

i -4 


46 

46 

21,1 

J 9-4 

I 7>7 

16,1 

H -5 

13,0 

11,5 

10,0 

8,5 

7 - 1 

5,6 

4,2 

2,8 

i -4 


44 

48 

20,4 

18,7 

I 7 n 

* 5-5 

1)4,0 

12,5 

1 1,0 

9,6 

8,2 

6,8 

5-4 

4 -i 

2-7 

•i ,3 


42 

50 

19,6 

18,0 

16,4 

* 4-9 

* 3-4 

1 2,0 

10,6 

9,3 

7,9 

6,6 

5-2 

3-9 

2,6 

i -3 


40 

52 

18,8 

17,2 

* 5-7 

! 4>3 

12,9 

11,4 

10,2 

8,9 

7>6 

6,3 

5 >° 

3-8 

2-5 

1,2 


38 

54 

17 >9 

16,5 

15,0 

13,6 

12,3 

1 1,0 

9-7 

8,5 

7,2 

6,o 

4,8 

3-6 

2.3 

1,2 


36 

5 6 

i 7 >i 

* 5-7 

H -3 

13,0 

11,7 

10,5 

9,2 

8,0 

6,9 

5.7 

4-5 

3-4 

2,2 

1,1 


34 

58 

16,2 

14,8 

* 3-5 

12,3 

1 1, 1 

9,9 

8,7 

7,6 

6,5 

5-4 

4-3 

3-2 

2,1 

1,1 


32 

60 

15,2 

14,0 

12,7 

1 1,6 

10,4 

9,3 

8,2 

7,2 

6,1 

5 -‘ 

4,0 

3 -° 

2,0 

1,0 


3 ° 

62 

> 4>3 

* 3-1 

12,0 

10,9 

9,8 

8,8 

7,7 

6,8 

5-8 

4,8 

3-8 

2,9 

i -9 

0,9 


28 

64 

1 3-4 

12,3 

1 1,2 

10,2 

9,2 

8,2 

7,z 

6-3 

5-4 

4-5 

3-5 

2.7 

i -7 

0,9 


26 

66 

12,4 

1 1,4 

10,4 

9,4 


7,6 

6 ,7. 

5,9 

5 >° 

4 - 1 

3-3 

2-5 

1,6 

0,8 


24 

68 

11,4 

10,5 

9-5 

8,7 

7-8 

7,0 

6,2 

5>4 

4,6 

3-8 

3 -° 

2-3 

i -5 

0,7 


22 

70 

10,5 

9,6 

8,7 

7-9 

7.1 

6,4 

5.6 

4,9 

4,2 

3-5 

2,8 

2,1 

i -4 

0,7 


20 

72 

9-4 

8,6 

7 >9 

7> 2 

6,5 

5,6 


4,4 

3-8 

3 -i 

2-5 

i >9 

1,2 

0,6 


18 

74 

8,4 

7>7 

7^° 

6,4 

5,8 

5 n 

4,5 

4,0 

3,4 

2,8 

2,2 

i -7 

1,1 

0,5 


16 

76 

7-4 

6,8 

6,2 

5.6 

5 n 

4 U 

4,0 

3U 

3,o 

2-5 

2,0 

i -5 

1,0 

0,5 


14 

78 

6-3 

5-8 

5-3 

4,8 

4-3 

3,9 

3,4 

3 ,° 

2,6 

2,1 

1-7 

i -3 

0,8 

0,4 


12 

80 

5-3 

4-9 

4-4 

4,0 

3,6 

3 , 2 

2,9 

2,5 

2,1 

1,8 

1-4 

1, 1 

0-7 

0-3 


xo 

82 

4>3 

3-9 

3-5 

3»2 

2,9 

2,6 

2,3 

2,0 

i ,7 

1,4 

1,1 

0,8 

0,6 

o-3 


8 

84 

3>2 

2,9 

2 -7 

2,4 

2,2 

1,9 

1,7 

i -5 

>,3 

1,1 

0,8 

0,6 

0,4 

0,2 


6 

86 

2,2 

1,9 

1,8 

i,6 

i -5 

i >3 

1,1 

1,0 

0,9 

o ,7 

0,6 

0,4 

°-3 

0,1 


4 

88 

1, 1 

1,0 

0,9 

0,8 

o ,7 

0,6 

0,6 

°,5 

0,4 

0,4 

o -3 

0,2 

0,1 

0,1 


2 

50 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

0,0 

e,o 


0 


Angle of 
the verti- 
cal with 


[ 3 ] 


of the Equatorial Instrument. 


123 


No. II. Table of the Effect of Parallax in North Polar Distance, 

and 

The horizontal parallax — 8 ',6. This correction is always — . 


Angle of 
the ver- 
tical and 
horary. 



DEGREES OF 

ALTITUDE. 




Angle of 
the ver- 
tical and 
horary. 


o° 

1 o° 

20° 

O 

O 

O 

O 

Tp 

O 

O 

'-O 

6o° 

O 

O 

IS. 

8 o° 

90° 


O 

u , 

// 

II 

II 

n 

II 

II 

It 

II 

II 

O 

O 

8,60 

8*47 

8,08 

7*45 

6*59 

5*53 

4 * 3 o 

z *94 

J *49 

0,0 

90 

IO 

8*4 7 

8*34 

7 * 9 6 

7*34 

6,49 

5*45 

4* 2 3 

2,90 

1,47 

0,0 

80 

20 

8,08 

7 * 9 6 

7,60 

7,00 

6,19 

5,20 

4»°4 

2*77 

1,40 

0,0 

70 

3 ° 

7*4 5 

7*34 

6,99 

6,45 

5.7 1 

4*79 

3 > 7 2 

2*55 

1,29 

0,0 

60 

40 

6,59 

6,49 

6,18 

5 * 7 ° 

5*°5 

4> 2 3 

3> 2 9 

2,26 

1*15 

0,0 

5 ° 

5 ° 

5*53 

5*44 

5 J 9 

4*79 

4> z 3 

3*55 

2,76 

1,89 

0,96 

0,0 

40 

60 

4 * 3 ° 

4* 2 3 

4*°4 

3 * 7 2 

3 * 3 ° 

2,76 

2,15 

*»47 

°*74 

0,0 

3 ° 

70 

2,94 

2,90 

2,77 

2 »55 

2,26 

1,89 

i *47 

1,01 

0,51 

0,0 

20 

80 

i ,49 

*»4 7 

1,40 

1,29 

1,14 

°»95 

°*75 

0,50 

0,26 

0,0 

IO 


Parallax in right ascension, x sec' declination. 

This correction is -f on the east, and — on the west side of the meridian*. 


No. III. Table of the Effect of Parallax in North Polar Distance, 

and A. 

The horizontal parallax being :r 10". This correction is always — . 


Angle of 
the ver- 
tical and 
horary. 



DEGREES OF 

ALTITUDE. 




Angle of 
the ver- 
tical and 
horary. 


o° 

IO° 

20° 

3 °° 

O 

O 

O 

O 

ui 

6o° 

O 

O 

8o° 

90° 


O 

II 

II 

II 

II 


// 

II 

a 

II 

II 

O 

O 

10,00 

9*85 

9,40 

8,66 

7*66 

6,43 

5,00 

3*42 

i *73 

0,0 

90 

IO 

9*85 

9*70 

9,26 

8*53 

7*54 

6.33 

4,92 

3*37 

1,70 

0,0 

80 

20 

9,40 

9> 2 5 

8,83 

8,14 

7,20 

6,04 

4 * 7 ° 

3,21 

1,63 

0,0 

70 

3 ° 

8,66 

8*53 

8,14 

7 * 5 ! 

6,64 

5*57 

4*33 

2,96 

1,50 

0,0 

60 

40 

7*66 

7*54 

7,20 

6,63 

5.87 

4*93 

3*83 

2,62 

1,32 

0,0 

5 ° 

5 ° 

6*43 

6,33 

6,04 

5.56 

4*92 

4 *i 3 

3,21 

2,21 

1, 1 1 

0,0 

40 

60 

5,00 

4*92 

4 * 7 ° 

4*33 

3*83 

3,21 

2*50 

i* 7 i 

0,86 

0,0 

3 ° 

70 

3*42 

3*37 

3*21 

2,96 

2,62 

2,20 

i* 7 i 

1,17 

o *59 

0,0 

20 

80 

i *73 

1,71 

1,63 

1,50 

i *33 

1, 11 

0,87 

°*59 

0,30 

0,0 

ia 


Parallax in right ascension, x sec' declination. 

This correction is + on the east, and — on the west side of the meridian. 


124 ? 


Sir George Shuckburgh's Account 


No, IV, 

Table of Natural Secants. 


Deg. 

Nat. 

sec. 

Deg. 

Nat. 

sec. 

Deg. 

Nat. 

sec. 

Deg. 

Nat. 

sec. 

Deg. 

Nat. 

sec. 

Deg. 

Nat. 

sec.. 

1 

10002 

16 

10403 

S 

3 1 

1 1666 

46 

1439 6 

6 1 

20627 

76 

4 ! 33 6 

2 

10006 

17 

10457 

3 2 

1 1792 

47 

14663 

62 

21301 

77 

44454 

3 

1 00 1 4 

18 

10515 

33 

1 1924 

48 

14945 

63 

22027 

78 

48097 

4 

10024 

19 

10576 

34 

12062 

49 

1 5 z 43 

64 

22812 

79 

52408 

5 

10038 

20 

10642 

35 

12208 

5 ° 

15557 

65 

23662 

80 

57588. 

6 

i °°55 

21 

1071 1 

36 

12361 

5 1 

15890 

66 

24586 

81 

63925 

7 

10075 

22 

10785 

37 

12521 

5 2 

16243 

67 

2 5 593 

82 

71853 

8 

10098 

2 3 

10864 

38 

12690 

53 

16626 

68 

26695 

83 

» 82055 

9 

10124 

24 

10946 

39 

12868 

54 

17013 

69 

2 79°4 

84 

95668 

io 

10154 

2 5 

11034 

4 ° 

*3054 

55 

J 7434 

70 

29238 

85 

1 H 737 

1 1 

10187 

26 

11126 

4 i 

13250 

56 

17883 

7 1 

30716 

86 

H 335 6 

12 

10223 

2 7 

11223 

4 2 

J 345 6 

57 

18361 

7 2 

32361 

87 

I 9 I °75 

13 

10263 

28 

1 1326 

43 

i 3 6 73 

58 

18871 

73 

34 2 03 

88 

286537 

H 

10306 

2 9 

1 1434 

44 

13902 

59 

19416 

74 

36280 

89 

572987 

J 5 

10353 

30 

1 1547 

45 

14142 

60 

20000 

75 

38637 

90 

Infinite 


of the Equatorial Instrument. 


12 5 


No, V. Table of the Correction of the Time, shewn by an 
Equatorial, on Account of Refraction, when the Instru- 
ment is not previously adjusted to the true Meridian. 


Angle of 
the 

vertical 
■with the 
horary 
circle. 


DEGREES OF ALTITUDE. 



7 ° 

IO° 

1 5 ° 

20° 

z 5 ° 

3 o° 

35 ° 

40° 

45 ° 

50° 

6o° 

7O 0 

8o° 


Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

fee. 

Sec. 

Sec. 

5 

338 ’ 

241, 

161,3 

118,9 

94,2 

74’9 

62, 

5**7 

43’7 

36,8 

2 5>3 

16,1 

8, 

lO 

169, 

1 20, 

80,7 

59’4 

47 ’ 

37>4 

3 *’ 

25,9 

21,9 

18,4 

1 2,6 

8,1 

4 > 

15 

I 14, 

8l, 

54-3 

40, 

31,8 

25,2 

20,9 

* 7»4 

* 4»7 

I 2,4 

8*5 

5*4 

2’7 

20 

86, 

61, 

4 1 ’ 

3°»4 

24,1 

19,1 

15,8 

13,2 

1 1,2 

9’4 

6,5 

4,1 

2,1 

2 5 

7 °- 

5 °’ 

33’4 

24,6 

1 9’5 

! 5’5 

1 2,8 

10,7 

9 >i 

7 » 6 

5’2 

3>3 

i ’7 

3 ° 

59 ’ 

42 ’ 

28,2 

20,6 

16,4 

1 3 » 

10,8 

9 ’ 

7,6 

6,4 

4-4 

2,8 

1 >4 

35 

5 1 ’ 

3 6 ’ 

24,4 

18, 

H >3 

1 1,4 

9’4 

7*8 

6,6 

5»6 

3 ’ 8 

2,4 

1,2 

40 

46, 

33 > 

21,8 

1 6, 

12,7 

10,1 

8,4 

7 > 

5>9 

5 ’ 

3»4 

2,2 

1,1 

45 

4 1 ’ 

3 °’ 

* 9-9 

14,6 

1 1,8 

9,2 

7’6 

6 ’3 

5 >4 

4’ 5 

3 ’i 

2, 

1, 

5 ° 

3 8 ’ 

2 7 » 

18,3 

I 3’4 

10,7 

8’5 

7 U 

5»9 

5 ’ 

4,2 

2,9 

1,8 

0, 

55 

36, 

26, 

17 ’* 

12,6 

10,1 

7’9 

6,6 

5’5 

4,6 

3>9 

2 ’7 

*»7 

0,9 

60 

34 ’ 

24, 

16,2 

11,9 

9’5 

7’5 

6,3 

5,2 

4’4 

3»7 

2,5 

1,6 

0,8 

6 5 

3 2 ’ 

2 3 ’ 

* 5’5 

1 1,4 

9 ’ 1 

7’2 

6, 

4>9 

4,2 

3’5 

2’4 

*’5 

0,8 

7 ° 

3 1 ’ 

22, 

* 4’9 

ii. 

8,8 

6,9 

5*8 

4,8 

4 ’ 

3-4 

2-3 

*»5 

°’7 

80 

3 °’ 

21, 

14,2 

10,5 

8-3 

6,6 

5’5 

4,6 

3>9 

3 > 2 

2.2 

i ,4 

0,7 

90 

29, 

21, 

* 4 ’ 

10,3 

8,2 

6 ’5 

5>4 

4’5 

3 ’ 8 

3 ’ 2 

2,2 

1,4 

o ,7 


X Secant of declination: 

This equation is — on the east, and -f on the west side of the meridian. 


lg(> 


Sir George Shuckburgh's Account 


No. VI. Table shewing the Correction of the Meridian 
Line, found by an Equatorial, arising from the Effect of 
Refraction, in Minutes and Decimals. 


Angle of 
the 

vertical 
with the 
horary 
circle. 

DEGREES OF ALTITUDE. 


7 ° 

10° 

15 0 

20° 

O 

N 

O 

O 

35 ° 

O 

O 

45 ° 

C*~| 

0 

0 

6o° 

O 

O 

80® 

o 

5 

4>5 

60,3 

40, 

29,8 

/ 

22,9 

18,3 

* 5»5 

12,6 

10,9 

9,2 

^3 

/ 

4 « 

2,3 

10 

4*>7 

2 9>7 

19,8 

14,8 

11,4 

9,1 

7,7 

6,2 

5,4 

4,5 

3 ,i 

2, 

I, I 

15 

2 7>3 

19.5 

13,1 

9>7 

7’5 

5,9 

5 , 

4,1 

3>5 

3, 

2, 

i ,3 

°>7 

20 

20,1 

H >4 

9,6 

7 , 2 

5’5 

4,4 

3,7 

3 , 

2,6 

2,2 

L 5 

1, 

°,5 

2 5 

15,8 

11,4 

7,6 

5 ’ 6 

4,3 

3,4 

2,9 

2,4 

2, 

J ’7 

1,2 

0,8 

0,4 

3 ° 

12,7 

9,1 

6,1 

4,5 

3,4 

2,8 

2 >3 

L 9 

1,6 

1,4 

0,9 

0,6 

°>3 

35 

10,2 

7>5 

5 > 

3,7 

2,8 

2 ’3 

1,9 

1,6 

i ,3 

1, 1 

0,8 

°,5 

°>3 

40 

8.7 

6,2 

4,2 

3 jI 

2,4 

J »9 

1,6 

1,3 

1, 1 

0,9 

0,6 

0,4 

0,2 

45 

7 > 3 

5,2 

3>5 

2,6 

2, 

1,6 

1,3 

1, 1 

0,9 

0,8 

0,5 

o ,3 

0,2 

5 ° 

6,1 

4,4 

2,9 

2,2 

i ,7 

i ,3 

1, 1 

0,9 

0,8 

0,6 

0,4 

°>3 

0,2 

55 

5 >i 

3,7 

2,4 

1,8 

i ,4 

1, 1 

0,9 

0,8 

0,7 

°>5 

0,4 

0,2 

0,1 

60 

4,2 

3 » 

2, 

i>5 

1, 1 

0,9 

0,8 

0,6 

°>5 

0,4 

°>3 

0,2 

0,1 

65 

3>4 

2,4 

i,6 

1,2 

0,9 

0,8 

0,6 

0,5 

0,4 

o ,3 

0,2 

0,2 

0,1 

70 

2,7 

J >9 

i »3 

0,9 

°>7 

0,6 

o,5 

0,4 

°>3 

°>3 

0,2 

0,1 

0,1 

80 

i >3 

0,9 

0,6 

°,5 

0,4 

°»3 

0,2 

0,2 

0,2 

0,1 

0,1 

0,1 

0, 

90 1 

0,0 j 

0, 

0, 

0, 

0, 

0, 

O, 

0, 

0, 

0, 

0, 

0, 

0, 


X Secant of the altitude. 

Note. If the observation is on the side of the meridian, then is the true meri- 
dian so many minutes to the of that found by the instrument. 


of the Equatorial Instrument t 


i»7 


No. VII. Table of the Effect of Refraction in Right As- 
cension in Time, when the Equatorial is adjusted to the 
Meridian. 


Angle of 
the 

vertical 
with the 
horary 
circle. 


DEGREES OF ALTITUDE. 



3 ° 

5 ° 

7 ° 

IO° 

15° 

20° 

25 0 

3 °° 

35 ° 

40 ° 

45 ° 

50 ° 

6o° 

7 °° 

8o° 

0 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

Sec. 

See. 

Sec. 

Sec. 

Sec. 

Sec. 

5 

5 >« 

3-5 

2 -5 

1.8 

1,2 

0,9 

°-7 

0,6 

0,5 

0,4 

°-3 

0.3 

0,2 

0,1 

0,1 

IO 

10,1 

6,9 

5 »! 

3-7 

2 -5 

1,8 

i -4 

I, I 

0,9 

0,8 

0-7 

0-5 

0,4 

0-3 

0,1 

IS 

! 5 > 

10,3 

7.6 

5-4 

3 - 6 

2-7 

2,1 

i -7 

1-4 

1.2 

I. 

0,8 

0,6 

0,4 

0,2 

20 

1 9-9 

* 3*5 

10, 

7 - 2 

4.8 

3-5 

2,8 

2,2 

1-9 

1-4 

1,2 

1. 1 

°-7 

°-5 

0,2 

25 

2 +>5 

16,6 

I 2 j 3 

8,8 

5-9 

4-3 

3-4 

2.7 

2-3 

1-9 

1,6 

i -3 

0,9 

0,6 

o -3 

3 ° 

29, 

1 9>7 

14-6 

10,5 

7 - 

5 > 2 

4-1 

3-3 

2-7 

2-3 

1,9 

i -7 

1, 1 

o -7 

0-3 

35 

33>4 

22,7 

16,8 

12, 

8, 

5-9 

4-7 

3-7 

3 - 1 

2,6 

2,2 

1,8 

i -3 

0,8 

0,4 

40 

37-4 

25,4 

18,6 

13.5 

9 - 

6 -7 

5-2 

4.2 

3-4 

2,9 

2,4 

2,1 

i -4 

0,9 

0,4 

45 

4*»3 

28, 

20,7 

14,9 

9-9 

7-3 

5-7 

4,6 

3-9 

3-2 

2-7 

2-3 

i -5 

1, 

0-5 

5 ° 

44-7 

3°»3 

22,5 

1 6,1 

10,7 

7-9 

6,2 

5 - 

4 - 1 

3-5 

2,9 

2-5 

!-7 

1, 1 

0,5 

55 

47 »7 

3 2 >4 

24, 

17,2 

1 U 5 

8,5 

6 -7 

5-3 

4-4 

3-7 

3 -i 

2-7 

1,8 

1, 1 

0,5 

60 

50.3 

34 . 2 

2 5-3 

18,1 

12,1 

8,9 

7 - 

5-7 

4-7 

3-9 

3-3 

2,8 

1,9 

1,2 

0,6 

65 

52,8 

35-9 

26,5 

19- 

12,8 

9-3 

7-4 

5-9 

4-9 

4-2 

3-5 

2,9 

2, 

!-3 

0,6 

70 

54,6 

37 - 

27,5 

i 9>7 

* 3 »i 

9-7 

7-7 

6,1 

5 -i 

4-3 

3-5 

3 - 

2,1 

i -3 

0,6 

80 

5 7 - 6 

39 > 1 

28,9 

20,7 

13,8 

10,1 

8, 

6,5 

5-3 

4-5 

3 - 8 

3-2 

2,2 

i -4 

°-7 

90 

58,4 

39 - 6 

2 9-3 

21, 

14- 

10,3 

8,2 

6-5 

5-4 

4-5 

3 - 8 

3-2 

2,2 

i -4 

°-7 


X Secant of declination. 

This correction is — cn the east, and -f- on the west side of the meridian. 


128 


Sir George Shuckburgh's Account, 


No. VIII. Table of the Effect of Refraction in Declination, 
when the Equatorial is adjusted to the Meridian. 


Angle of 
the 

vertical 
with the 
horary 
circle. 


DEGREES OF ALTITUDE. 



3 

0 

5 

0 


7 ° 

IO° 

15° 

20° 

2 5 ° 

3 °° 

35 ° 

O 

O 

45 ° 

O 

O 

LO 

60° 

0 

0 

8o° 

o 

/ 

// 

/ 

// 

, 

u 


// 

1 

// 

/ 

// 


// 

/ 

// 

/ // 

/ u 

II 

// 

II 

n 

H 

o 

14 

3 6 

9 

54 

1 

20 

5 

15 

3 

3 ° 

2 

35 

2 

2 

1 

38 

1 21 

1 8 

57 

48 

33 

21 

10 

IO 

H 

2 4 

9 

46 

7 

H 

5 

1 1 

3 

27 

2 

3 2 

2 


1 

37 

i 20 

1 7 

57 

48 

33 

21 

10 

20 

13 

39 

9 

16 

6 

5 2 

4 

56 

3 

17 

2 

26 

1 

55 

1 

3 2 

1 16 

1 4 

53 

45 

3 1 

20 

9 

2 5 

13 

12 

8 

59 “ 

38 

4 

45 

3 

10 

2 

20 

1 

5 ° 

1 

29 

1 14 

1 2 

5 2 

44 

3 ° 

l 9 

9 

3 ° 

12 

35 

8 

33 6 

20 

4 

3 2 

3 

1 

2 

H 

1 

45 

1 

2 5 

i 10 

59 

49 

42 

2 9 

18 

9 

35 

1 1 

55 

8 

6 6 


4 

18 

2 

5 2 

2 

7 

1 

40 

i 

20 

1 6 

56 

46 

39 

2 7 

17 

8 

40 

1 1 

1 1 

7 

35 

5 

37 

4 

1 

2 

40 

1 

59 

1 

33 

1 

15 

1 2 

5 2 

43 

37 

2 5 

16 

8 

45 

10 

1 9 

7 


5 

1 1 

3 

43 

2 

28 

1 

5 ° 

1 

26 

1 

9 

58 

48 

40 

34 

2 3 

15 

7 

5 ° 

9 

22 

6 

21 

4 

42 

3 

22 

2 

J 5 

1 

40 

1 

18 

1 

3 

5 2 

44 

36 

3 i 

21 

H 

6 

55 

8 

21 

5 

40 

4 

1 2 

3 


2 


1 

2 9 

1 

10 


56 

46 

39 

33 

2 7 

l 9 

12 

6 

60 

7 

16 

4 

5 6(3 

39 

2 

37 

1 

45 

1 

18 

1 

1 


49 

40 

34 

2 9 

24 

1 6 

1 1 

5 

6 5 

6 

7 

4 

9p 

4 

2 

1 2 

1 

28 

1 

5 


5 i 


4 1 

34 

28 

2 4 

20 

*4 

9 

4 

70 

4 

58 

3 

22 

2 

3 ° 

I 

48 

1 

12 


53 


42 


33 

28 

2 3 

19 

16 

1 1 

7 

3 

75 

3 

45 

2 

34 

1 

54 

1 

21 


54 


40 


3 2 


2 5 

21 

18 

J 5 

12 

9 

6 

3 

80 

2 

3 2 

1 

43 

1 

16 


55 


37 


27 


21 


17 

14 

12 

10 

8 

6 

4 

2 

85 

1 

1.6 


5 2 

1 

38 


27 


18 


13 


1 1 


9 

7 

6 

5 

4 

3 

2 

1 










t 




Fhflos.Trans. MDCCXCIII . Tah.X-f?. ns. 




One t7iire7 t7ie ei'ze of rfic Ortfftnal. 


One 7/e/7f t7n etze of (fie Ortyinal 




Philos. Trans. MDCCXCIE. Tab. XI. p.n 8 . 







Philo 's. Trans. MDCCXCIH. Tab. XII. p. ns. 



J-Tjji. rp. Jc. 








Philos. Trans. MDCCXCIU Tab. XIII. p. ns. 





F/it7m- Tram-. ftlDCCXCW. Tab JOW a., it,. 





C I2 9 H 


XI. Additional Observations on the Method of making Ice at 
Benares. In a Letter to William Marsden, Esq. F. R. S. 
from John Lloyd Williams, Esq. of Benares. 

Read May 2, 1793. 


DEAR SIR, 

In addition to what I have already communicated to you, 
respecting the mode of procuring ice in this country, the 
following observations on that subject, accompanied with 
some account of the temperature of the air, and state of the 
thermometer, may not be unacceptable. 

April 30th, 1792, the thermometer, in the shade, being at 
95 degrees, some water was taken up from a well, sixty feet 
deep, and the thermometer being immerged in it, its tem- 
perature was found to be 74, degrees. This water was then 
poured into four pots, or pans, similar to those which, in my 
former letter, I mentioned as being employed in the process 
for making ice. They were also similar to each other in size 
and construction, except that two of them were new and un- 
glazed, and the two others old, with their pores closed, so that 
no moisture could transpire through them. These pots were 
then exposed to a hot westerly wind, in the shade, for the 
space of three hours ; viz. from two o'clock in the afternoon 
till five. Upon examining them at that time, the water in 

S 


MDCCXCIII. 


1 3 ° 


Mr. Williams's additional Observations 


the old pots was found to be at 84 degrees, and that in the 
new, or porous ones, at 68. After remaining in that situa- 
tion one hour longer, the water in the old pots rose to 88 
degrees, whilst that in the new ones continued at 68. 

May 1st, at two o'clock in the afternoon, the thermo- 
meter then being, in the sun, at 110 degrees, and in the 
shade at 100, the experiment was repeated, with the same 
pots as before. After being filled with well-water, they were 
exposed for four hours, viz. from two o'clock till six, to a hot 
wind ; the water in the old pots was then found to be at 
97 degrees, that in the new ones at 68. 

The foregoing observations on the frigorific effect of eva- 
poration from porous vessels, will perhaps account, in some 
measure, for ice being formed when the thermometer, in the 
air, is above the freezing point. And the power of evapora- 
tion in generating cold, may be further elucidated by the fol- 
lowing observations on the effects produced, by its means, in 
our houses. 

May 16, 1792, at two in the afternoon. 

The thermometer, in the sun, with a hot westerly wind, 
rose to - - - -118 degrees. 

Ditto, in the shade, but exposed to the hot 

wind - - - 110 ditto. 

Ditto, in the house, which was kept cool by . 

tatties - - - - 87 ditto. 


June 7. 

Thermometer, in the sun 

Ditto, in the shade, and hot wind 

Ditto, in the house, cooled by tatties 


1 13 degrees. 
104 ditto. 

83 ditto. 


on the Method of making Ice at Benares. 131 

Tatties are a kind of mat, made of fresh green bushes, or 
long roots, like snake-root ; they are affixed to the door or 
window frames, and kept constantly sprinkled with water. 
The degree of cold produced by their means is supposed to 
be in proportion to the heat of the wind which passes through 
them, as on that depends the quantity of evaporation. 


Benares, 

October i, 1792. 


I am, &c. 


J. LL. WILLIAMS. 


- 


■ 

— _ 








■' \ 




' 
















METEOROLOGICAL JOURNAL, 

KEPT AT THE APARTMENTS 

OF THE.- 

ROYAL SOCIETY, 


BY ORDER OF THE 


PRESIDENT AND COUNCIL. 


C 2 3 


METEOROLOGICAL JOURNAL 


for January, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter* 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Sir. 

Jan. 1 

8 

O 

44 

53 

2 9’3 4 

80 

O 

d 

SSE 

1 

Cloudy. 


2 

0 

44 

57*5 

29,38 

78 


E 

1 

Cloudy. 

2 

8 

0 

4 1 

5 2 

2 9’«7 

83 

0,125 

NE 

1 

Rain. 


2 

0 

43.5 

55 

2 9’95 

74 


NNE 

2 

Cloudy. 

3 

8 

0 

3 6 U 

5 2 

30,14 

73 


N 

1 

Cloudy. 


2 

0 

43 

55 

30,14 

73 


NE 

1 

Cloudy. 

4 

8 

0 

38 

5 2 

30,35 

77 


NNE 

1 

Cloudy. 


2 

0 

42 

55,5 

30,38 

73 


NNE 

1 

Cloudy. 

5 

8 

0 

38 

5 2 

30,47 

77 


N 

1 

Cloudy. 


2 

0 

39,5 

54,5 

30,46 

7 1 


NNW 

1 

Cloudy. 

6 

8 

0 

35 

52 

30,42 

75 


NNE 

1 

Cloudy. 


2 

0 

38,5 

5 4-- 5 

30,33 

7 ° 


NNE 

1 

Cloudy. 

7 

8 

O 

40 

5 M 

30,1 1 

77 


W 

1 

Cloudy. 


2 

0 

44 

55 

30,00 

72 


WNW 

1 

Cloudy. 

8 

8 

0 

3 i 

5 ° 

30,15 

69 


NE 

1 

Cloudy. 


2 

0 

36 

54 G 

3°, 1 '8 

65 


NE 

1 

Fine. 

9 

8 

0 

33 

5 ° 

29,80 

7 ° 


WNW 

1 

Cloudy. 


2 

O 

38 

53,5 

2 9,55 

75 


WNW 

1 

Cloudy. 

10 

8 

0 

34.5 

5 ° 

29,36 

73 

0,060 

WNW 

1 

Cloudy. 


2 

O 

3 6 

53.5 

29,36 

75 


E 

1 

Cloudy. 

1 1 

8 

0 

2 5 

46 

29,27 

68 


NE 

1 

Fair. 


2 

0 

29 

48 

29,21 

60 


NE 

1 

Fine. 

12 

8 

O 

19 

44 

29,21 

67 


WNW 

1 

Fine. 


2 

O 

28 

46,5 

29,25 

65 


WNW 

1 

Fine. 

13 

8 

O 

20 

44 

29,64 

69 


WNW 

1 

Hazy. 


2 

O 

28 

45>5 

29,71 

63 


WNW 

1 

Fme. 

H 

8 

O 

24 

43 

29,67 

7 ° 


E 

2 

Fine. 


2 

O 

3 ° 

44,5 

29,44 

64 


E 

2 

Cloudy. 

15 

8 

O 

4 ° 

4+>5 

29,06 

92 

0,040 

S 

2 

Rain. 


2 

O 

43 

48 

28,98 

85 


SSE 

2 

Cloudy. 

16 

8 

O 

4 1 

4 6 ’5 

29,1 1 

82 

0,015 

S 

2 

Cloudy. 


2 

O 

43 

49’ 5 

29,13 

81 


s 

2 

Rain. ; 


* These observations were made with Mr. De Luc’s hygrometer, described in 
Vol. LXXXI. of the Phil. Trans, p. 420. 


[ 3 3 


METEOROLOGICAL JOURNAL 
for January, 1792. 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 


1792 



without. 

within. 


gro- 

me- 




Weather.- 











H. 

M. 

O 

0 

Inches. 


Inches. 

Points. 

Str. 


Jan. 17 

8 

O 

42 

48,5 

29,25 

* 

0,074 

ENE 

1 

Foggy. 


2 

O 

45 

5 2 

29,42 



NNE 

1 

Cloudy. 

18 

8 

O 

34 

4 8 >5 

29,88 



NE 

1 

Fair. 


2 

O 

37 

5 I >5 

29,92 



NE 

1 

Fair. 

19 

8 

O 

3 2 

48 

30,00 



NE 

1 

Cloudy. 


2 

O 

3 6 

49>5 

30,00 



ENE 

1 

Cloudy. 

20 

8 

O 

33 

48 

3°,°4 



ENE 

1 

Cloudy. 


2 

O 

34 

48 

29,96 



E 

1 

Cloudy. 

21 

8 

O 

3 2 

47 

29,80 



E 

1 

Cloudy. 


2 

O 

3 6 

49 

29,83 



E 

1 

Cloudy. 

22 

8 

O 

35 

48 

29,85 



E 

1 

Foggy. 


2 

O 

40 

5 ° 

2 9,75 



E 

1 

Cloudy. 

2 3 

8 

O 

33 

47 

2 9»47 


0,268 

WNW 

1 

Cloudy. 


2 

O 

3 6 >5 

5 ° 

29,56 



WNW 

1 

Cloudy. 

24 

8 

0 

4 2 

48 

29,57 


°.°55 

Ssw 

1 

Foggy. 


2 

O 

47 

5 « 

29,46 



S 

2 

Cloudy. 

2 5 

8 

O 

47 

5 i 

29,20 


0,340 

SW 

2 

Cloudy; much wind 


2 

O 

5 i 

55 

29,32 



SW 

2 

Cloudy, [last night. 

26 

8 

O 

48 

52,5 

29,01 


°> 1 45 

SW 

2 

Cloudy ; much wind 


2 

O 

5 ° 

54-5 

28,94 



SW 

2 

Cloudy, [last night. 

2 7 

8 

O 

46 

53»5 

20,48 


0,130 

wsw 

1 

Cloudy. 


2 

O 

5 ° 

57»5 

2 9.57 



w 

2 

Cloudy. 

28 

8 

O 

4 2 

53 

29,52 



F, 

1 

Cloudy. 


2 

O 

48 

57 

29,35 



SW 

1 

Rain. 

2 9 

8 

O 

46 

55 

29.55 


0,195 

ssw 

1 

Cloudy. 


2 

O 

48 

57 

29,46 



ssw 

I 

Cloudy. 

3 ° 

8 

O 

43 

55 

29,75 


0,120 

SW 

1 

Cloudy. 


2 

O 

5 ° 

57 

29.74 



SW 

2 

Cloudy. 

3 1 

8 

O 

48 

55 

29,52 



SW 

1 

Fair. 


2 

O 

53 

57>5 

29.53 


p 

CO 

SW 

2 

Fine. 


* This interruption, in the observations of the hygrometer, was occasioned by 
one end of the whalebone having slipped out of the pincers by which it is heldo 


C 4 3 


METEOROLOGICAL JOURNAL 


for February, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Rarom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

Feb. 1 

8 

O 

47 

5 6 

29 ,66 



sw 

1 

Fair. 


2 

O 

5 2 

53 

29,80 



WNW 

1 

Fair. 

2 

8 

O 

5 ° 

56 

29,90 



SW 

2 

Cloudy. 


2 

O 

5 2 >5 

58 

29,84 



SW 

2 

Cloudy. 

3 

8 

O 

40 

56 

30>05 



w 

1 

Fine. 


2 

O 

47 

57 

30,10 



w 

2 

Cloudy. 

4 

8 

O 

35 

55 

30,29 



w 

1 

Fair. 


2 

O 

43 

58,5 

3°, 2 9 



NW 

1 

Fine. 

5 

8 

O 

37 

54 

30,17 



E 

1 

Foggy. 


2 

O 

43 

55 

3°> l 3 



ESE 

1 

Fair. 

6 

8 

O 

37 

53 

30,00 



E 

1 

Cloudy. 


2 

O 

45 

55 

29,95 



ssw 

1 

Cloudy. 

7 

8 

O 

48 

53>5 

29,75 


0,095 

sw 

2 

Cloudy. 


2 

O 

505 

50,5 

29,70 



sw 

2 

Cloudy. 

8 

8 

O 

43 

54 

29,67 


0,295 

wsw 

1 

Fair. 


2 

O 

49*5 

57 

29,83 



wsw 

1 

Fair. 

9 

8 

O 

40 

55 

3 °’ 3 ° 



N 

1 

F’air. 


2 

O 

43 

56,5 

30,40 



w 

1 

Cloudy. 

10 

8 

O 

43 

54’5 

30,40 



sw 

1 

Cloudy. 


2 

O 

48 

57 

3 °, 36 



wsw 

1 

Cloudy. 

1 1 

8 

O 

44 

55 

30,18 



SWbyW 

1 

Cloudy. 


2 

O 

5 ° 

58 

30,16 



wsw 

1 

Cloudy. 

12 

8 

C 

46 

5 6 

3 °> l6 



wsw 

1 

Fair. 


2 

O 

56 

58,5 

30,18 



wsw 

1 

Fine. 

13 

8 

O 

4 i 

57 

30,26 



wsw 

1 

Fine. 


2 

O 

5 2 

60 

30,26 



wsw 

! 

Fine. 

14 

8 

O 

37 

5 6 

30,22 



WNW 

I 

Fair. 


2 

O 

44 

58 

30,22 



WNW 

I 

Hazy. 


8 

O 

37 

55 

30,06 



w 

I 

Foggy. 


2 

O 

45 

57>5 

30,04 



E 

I 

F air. 

16 

8 

O 

36 

54 

3 °, 17 



NE 

I 

Cloudy. 


2 

O 

38 

5 6 

30, 22 



NE 

I 

Cloudy. 


C 5 3 


i 



< 


METEOROLOGICAL JOURNAL 
for February, 1792. 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 





1792 






me- 




Weather. 











H. 

M. 

O 

O 

Inches. 


Inches. 

Points. 

Str. 


Feb. 17 

8 

O 

26 

5 1 

3 °, 4° 



NNE 

2 

Fair. 


2 

O 

3 2 

53 

30,28 



NE 

2 

Fair. 

18 

8 

O 

2 3 

47 

29,98 



NNE 

2 

Fair. 


2 

O 

26,5 

49*5 

30,00 



NNE 

2 

Fine. 

l 9 

8 

O 

3 ° 

4 6 *5 

29>70 



NNE 

2 

Cloudy. 


2 

O 

3 2 

48,5 

29,62 



E 

1 

Snow. 

20 

8 

O 

22,5 

44 

2 9>53 



NE 

1 

Snow. 


2 

O 

26 

47 

29*63 

49 


NNW 

1 

Fine. 

2 1 

8 

O 

16,5 

43 

29,78 

59 


WNW 

1 

Hazy. 


2 

O 

29 

46 

29*77 

52 


W 

1 

Fair. 

22 

8 

O 

3 i 

43*5 

29,59 

73 


NW 

1 

Hazy. 


2 

O 

34*5 

48 

29,72 

59 


WNW 

1 

Fair. 

2 3 

8 

O 

2 7 

44 

29,88 

67 


W 

1 

Hazy. 


2 

O 

33 

48 

29*93 

60 


E 

1 

Fine. 

24 

8 

O 

3 ° 

44.5 

29,86 

6 5 


E 

1 

Cloudy. 


2 

O 

37 

47 

29,80 

61 


E 

1 

Rain. 

2 5 

8 

O 

3 8 *5 

4 6 

29,84 

90 

0,120 

E 

1 

Cloudy. 


2 

O 

4 ! *5 

47»5 

29,77 

8 7 


E 

1 

Cloudy. 

26 

8 

O 

43»5 

48 

29,61 

90 

0,202 

SE 

1 

Cloudy. 


2 

O 

5 i 

5 1 

29,64 

79 


SSW 

2 

Cloudy. 

2 7 

8 

O 

42 

49 

29,89 

86 


SW 

2 

Fine. 


2 

O 

49 

5 2 ,5 

29*94 

68 


SW 

1 

Cloudy. 

28 

8 

O 

40 

5 ° 

30,02 

82 


ENE 

1 

Cloudy. 


2 

O 

49 

53 

30,04 

64 


ESE 

1 

Hazy. 

29 

8 

O 

40 

5 2 

29,99 

74 


E 

1 

Cloudy. 


2 

O 

47 

54 

29,95 

7 1 


SE 

1 

Cloudy. 


b 


C 6 3 


METEOROLOGICAL JOURNAL 


for March, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter'. 

Rain. 

Wind 

s. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

Mar. 1 

7 

O 

43 

5 2 

29,80 

85 


E 

I 

Foggy. 


2 

O 

5 ° 

55 

29,66 

64 


ESE 

2 

Cloudy. 

2 

7 

O 

47 

52,5 

29,45 

76 


E 

I 

Cloudy. 


2 

O 

5 1 

5 6 

29,45 

79 


S 

I 

Rain. 

3 

7 

O 

43 

55 

29,58 

84 

0,050 

ssw 

I 

Cloudy. 


2 

O 

50 

57 

29,57 

o 4 


ssw 

2 

Cloudy. 

4 

7 

O 

48 

54 

29,14 

79 

0,091 

s 

2 

Rain. 


2 

O 

5 ° 

57 

29,07 

77 


ssw 

2 

Cloudy. 

5 

7 

O 

45 

55 

29,40 

77 

0,510 

sw 

1 

Cloudy. 


2 

O 

46 

56 

29,58 

6 3 


WNVV 

1 

Cloudy. 

6 

7 

O 

4 i 

53 

29,44 

75 


s 

2 

Rain. 


2 

O 

48 

53 

2 9>37 

53 


wsw 

2 

Fine. 

7 

7 

O 

37 

5 3 ’5 

29,44 

70 

0,129 

w 

1 

Fine. 


2 

O 

40 

55 

29,50 

67 


wsw 

1 

Rain. 

8 

7 

O 

34 

52 

29,57 

6 3 

0,231 

WNW 

1 

Fair. 


2 

O 

40 

54 

29,64 

55 


NW 

1 

Cloudy. 

9 

7 

O 

26 

50 

29,91 

64 


NNE 

1 

Fair. 


2 

O 

33 

52 

29,98 

55 


NNE 

1 

Cloudy. 

10 

7 

O 

26 

48,5 

3 °A 3 

6 5 


NNE 

1 

Fine. 


2 

O 

34 

48 

3 0 ’ 1 8 

54 


NNE 

1 

Fine. 

1 1 

7 

O 

28 

4 6 ,5 

30,26 

64 


NNE 

1 

Fine. 


2 

O 

3 6 

48.5 

3 °’ 3 1 

5 i 


NNE 

1 

Fair. 

12 

7 

O 

29 

'47 

3°>49 

63 


ENE 

1 

Fair. 


2 

O 

3 6 

5 i 

3°--5 1 

5 1 


E 

1 

Fine. 

!3 

7 

O 

3 ° 

46 

30,23 

6 1 


E 

1 

Cloudy. 


2 

O 

4 ° 

48,5 

29,91 

53 


SE 

1 

Cloudy. 

H 

7 

O 

4 1 

47 

29,58 

86 

0,067 

SW 

1 

Cloudy. 


2 

O 

49 

5 i 

29,54 

57 


wsw 

1 

Cloudy. 

J 5 

7 

O 

43 

49 

29,41 

78 

°» I 34 

WNW 

1 

Fair. 


2 

O 

47 

52 

29,40 

61 


w 

1 

Cloudy. 

16 

7 

O 

38 

50 

29,86 

7 6 


w 

1 

Fair. 


2 

O 

5 1 

54 

2 9’93 

65 


w 

1 

Fair. 


L 7 J 





METEOROLOGICAL JOURNAL 
for March, 1792 . 



Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 











me- 





1 7 92 












H. 

M. 

O 

O 

Inches. 


Inches. 

Points. 

Str. 


Mar. 1 7 

7 

O 

47 

54 

29,83 

79 


SW 

2 

Cloudy. 


2 

O 

52 

5 6 

29,82 

74 


sw 

2 

Cloudy. 

18 

7 

O 

49 

54 

29,66 

7 ° 


SW 

2 

Cloudy. 


2 

O 

5 3 >5 

57 

29,75 

57 


sw 

2 

Fair. 

*9 

7 

O 

3 * 

53>5 

3°> I 2 

70 

0,034 

w 

I 

Fine. 


2 

O 

5 ° 

58 

3 °, 19 

48 


w 

I 

Fine. 

20 

7 

O 

42 

53>5 

30,19 

65 


s 

2 

Fine. 


2 

O 

5 ° 

57 

30,12 

49 


S by W 

2 

Fine. 

21 

7 

O 

43 

54 

30,08 

76 

0,041 

SW 

I 

Cloudy. 


2 

O 

53 

57>5 

30,11 

53 


WNW 

I 

Cloudy. 

22 

7 

O 

43 

54»5 

30,0a 

5 6 


WNW 

I 

Cloudy. 


2 

O 

5 1 

57>5 

3°,°5 

57 


NW 

I 

Fair. 

23 

7 

O 

43 

55 

29,87 

6 l 


SW 

2 

Cloudy. 


2 

O 

53 5 

5 « 

29,82 

54 


wsw 

2 

Fair. 

24 

7 

O 

47>5 

57 

29,80 

6 5 


SSW 

2 

Cloudy. 


2 

O 

5 ° 

57>5 

29,69 

68 


ssw 

2 

Cloudy. 

25 

7 

O 

5 1 

57 

29,50 

76 

0,074 

sw 

2 

Cloudy. 


2 

O 

54>5 

59 

29,56 

50 


sw 

2 

Cloudy. 

26 

7 

O 

47 

56,5 

29,60 

66 

°,°55 

sw 

2 

Fair. 


2 

0 

52 

58»5 

29,58 

52 


w 

2 

Cloudy. 

27 

7 

O 

44 

5 6 

29,48 

70 

0,103 

ssw 

2 

Cloudy. 


2 

O 

49>5 

5 8 >5 

29,49 

62 


sw 

2 

Fair. 

28 

7 

O 

43 

56 

29>74 

6 5 

0,082 

w 

1 

Fine. 


2 

O 

52 

59 

29,84 

S 2 


sw 

1 

Cloudy. 

29 

7 

O 

47 

57 

29,70 

60 


SSE 

2 

Fine. 


2 

O 

5 6 

61 

29,61 

5 ° 


SSE 

2 

Fine. 

3° 

7 

O 

44 

58 

29,66 

67 

0,140 

wsw 

1 

Cloudy. 


2 

O 

4 6 

59>5 

29,72 

6 5 


s 

2 

Cloudy. 

3 1 

7 

O 

42 

57 

30,00 

65 

0,050 

w 

1 

Fair. 

. — - 

2 

0 

52 

60 

29,90 

60 


sw 

2 

Cloudy. 


b 2 


C 8 3 


1 





METEOROLOGICAL JOURNAL 
for April, 1792. 

* 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 











me- 




Weather. 

* 79 2 











H. 

M. 

0 

0 

Inches. 

Lei • 

Inches. 

Points. 

Str. 


Apr. i 

7 

o 

5 2 

57,5 

29,70 

75 

0,039 

sw 

2 

Cloudy. 


2 

o 

54 

60,5 

29,65 

7 ° 


sw 

2 

Cloudy. 

2 

7 

o 

48 

58 

29,59 

66 


w sw 

2 

Cloudy. 


2 

o 

5 2 >5 

60 

29,64 

64 


sw 

2 

Cloudy. 

3 

7 

o 

39’5 

57>5 

29,^6 

67 

0,048 

w 

1 

Fair. 


2 

o 

5 ° 

5 « 

29,80 

5 1 


SW by S 

2 

Cloudy. 

4 

7 

o 

48 

57 

2 9>43 

69 

0,205 

w 

1 

Fine. 


2 

o 

55 

59 

29,38 

6 5 


WNW 

2 

Cloudy. 

5 

7 

o 

42 

57 

29,42 

6 5 

0,117 

WNW 

1 

Fine. 


2 

o 

5 2 

58.5 

29,50 

5 2 


WNW 

2 

Fair. 

6 

7 

o 

43 

56.5 

29,94 

6 3 


NW 

1 

Cloudy. 


2 

o 

5 2 

59 

30.13 

51 


NW 

2 

Fair. 

7 

7 

o 

4 M 

57>5 

30,30 

62 


WNW 

1 

Fine. 


2 

o 

53 

60,5 

3 °. 3 2 

45 


s 

2 

Fine. 

8 

7 

o 

48 

57 

30,22 

5 i 


SSE 

1 

Hazy. 


2 

o 

55 

61 

30,16 

45 


SE 

1 

Fair. 

9 

7 

o 

47 

59 

30,07 

60 


E 

1 

Fair. 


2 

o 

57 

60,5 

30,05 

53 


E 

1 

Hazy. 

IO 

7 

o 

5 2 

60 

30,00 

61 


ENE 

1 

Fair. 


2 

o 

60,5 

6 3 

29,98 

44 


E 

1 

Fine. 

1 1 

7 

o 

49,5 

60,5 

30,01 

61 


ENE 

1 

Fine. 


2 

o 

6 3 

6 5,5 

30,00 

44 


E 

1 

Fine. 

12 

7 

o 

5 2 

62 

30,05 

62 


E 

1 

Fine. 


2 

o 

62 

64 

30,02 

54 


SE 

. 1 

Fair. 

>3 

7 

o 

57 

6 3 

29,98 

59 


E 

1 

Cloudy. 


2 

o 

66 

64,5 

29,98 

61 


W 

1 

Fair. 

H 

7 

o 

55 

6 3 

30,01 

60 


W 

1 

Cloudy. 


2 

o 

6i -5 

6 3>5 

30,01 

59 


w 

1 

Hazy. 

is 

7 

o 

5 2 

62 

29,98 

61 


ENE 

2 

Cloudy. 


2 

o 

57 

61,5 

29,94 

5 6 


ENE 

2 

Hazy. 

16 

7 

o 

48 

60 

2 9,93 

61 


ENE 

2 

Fair. 


2 

o 

56,5 

61 

29,89 1 56 


ENE 

2 

Fair. 


C 9 ] 


METEOROLOGICAL JOURNAL 
for April, 1792. 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 





T 702 






me- 




Weather. 

1 ly* 






ter. 





H. 

M. 

O 

O 

Inches. 


Inches. 

Points. 

Str. 


Apr. 17 

7 

O 

52 

60 

29,70 

5 6 


ENE 

2 

Cloudy. 


2 

O 

S 3 

59 

29,62 

t>2 


E 

1 

Cloudy. 

18 

7 

O 

47 

58,5 

29,26 

70 

0,251 

WNW 

1 

Rain. 


2 

O 

48 

60 

29,12 

6 7 


WNW 

1 

Cloudy. 

19 

7 

O 

4 i 

57 

29,21 

70 

0,552 

NW 

1 

Rain. 


2 

O 

42,5 

57 

2 9’33 

70 


N 

2 

Rain. 

20 

7 

O 

38 

56 

29,87 

66 

O 

u, 

O 

N 

1 

Fine. 


2 

O 

44>5 

55>5 

30,07 

55 


N 

2 

Cloudy. 

21 

7 

O 

42 

55 

30,23 

60 


W 

2 

Cloudy. 


2 

O 

5 i.S 

57 

30,22 

5 ° 


sw 

2 

Fair. 

22 

7 

O 

48 

54>5 

30,04 

05 


sw 

2 

Cloudy. 


2 

O 

55 

57.5 

30,03 

59 


sw 

2 

Cloudy. 

23 

7 

O 

49 

56,5 

29,82 

59 


sw 

2 

Fine. 


2 

O 

60,5 

59.5 

29,77 

47 


ssw 

2 

Fine. 

24 

7 

O 

5 L 5 

58 

29,72 

6 5 


NE 

1 

Cloudy. 


2 

O 

52,5 

59>5 

2 9>73 

66 


NW 

1 

Cloudy. 

2 S 

7 

O 

43 ’5 

58 

29,89 

67 

O 

OO 

OO 

W 

1 

Fine. 


2 

O 

5 5>5 

60 

29,96 

47 


W 

1 

Fine. 

26 

7 

O 

46 

58 

30,17 

66 


W 

1 

Fair. 


2 

O 

58,5 

60,5 

30,17 

47 


W 

1 

Fine. 

27 

7 

O 

52 

59 

30,15 

61 


sw 

2 

Cloudy. 


2 

O 

57 

61,5 

30,18 

59 


sw 

2 

Cloudy. 

28 

7 

O 

54>5 

59.5 

30,23 

6 5 


sw 

2 

Cloudy. 


2 

O 

60 

60,5 

30,28 

59 


sw 

2 

Cloudy. 

29 

7 

O 

5 6 

60 

30,30 

63 


sw 

1 

Fair. 


2 

O 

62 

61 

30,26 

55 


NE 

1 

Fine. 

3° 

7 

O 

54 

60,5 

30,01 

64 


NE 

1 

Hazy. 


2 

O 

6 3 

6 3 

29,86 

62 


NE 

1 

Fair. 


C 10 3 


METEOROLOGICAL JOURNAL 


for May, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 
g IO- 
me- 
ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

May 1 

7 

O 

45 

59=5 

2 9’93 

61 

0,070 

W 

1 

Fair. 


2 

O 

53 

59=5 

29,99 

43 


WNW 

2 

Fair. 

2 

7 

O 

46 

58=5 

3 °> I 5 

56 


WNW 

1 

Fine. 


2 

O 

53 

59 

3°,sS 

44 


NW 

1 

F air. 

3 

7 

O 

4 2 =5 

57=5 

3 °= 3 S 

55 


WNW 

1 

Fine. 


2 

O 

52 

58 

3 °= 3 2 

44 


W N W 

i 

fine. 

4 

7 

O 

49 

58 

30,06 

65 


WNW 

1 

Cloudy. 


2 

O 

53 

58 

29,88 

6 S 


WNW 

2 

Cloudy. 

5 

7 

O 

43 

56 

30 =H 

60 

O 

d 

N 

2 

Fair. 


2 

0 

5 ° 

56,5 

30=13 

57 


NE 

2 

Cloudy. 

6 

7 

O 

45 ’5 

55=5 

30,18 

62 


NE 

2 

Fine. 


2 

O 

55 

57 

30=16 

5 ° 


NE 

2 

Fair. 

7 

7 

O 

46,5 

54=5 

30,06 

61 


NE 

2 

Fine. 


2 

O 

57=5 

5 6 =5 

30,01 

45 


NE 

2 

Fair. 

8 

7 

O 

46 

56 

30,06 

60 


NE 

2 

Fine. 


2 

O 

54’5 

58 

30,02 

53 


NE 

2 

Fine. 

9 

7 

O 

47 

56,5 

30,03 

60 


NE 

2 

Cloudy. 


2 

O 

52,5 

5 <M 

30,05 

5 2 


NE 

2 

Cloudy. 

10 

7 

O 

44=5 

55=5 

30,12 

58 


NE 

1 

Cioudy. 


2 

O 

47 ’5 

• 54=5 

30=13 

55 


NE 

1 

Cioudy. 

1 1 

7 

O 

44 

54 

30,17 

55 


NE 

1 

Cioudy. 


2 

O 

5°=5 

54 

30,16 

45 


NE 

1 

Cloudy. 

12 

7 

O 

45 

54 

30=16 

54 


N 

1 

Cloudy. 


2 

O 

52,5 

54=5 

30,18 

47 


NW 

1 

Cloudy. 

1 3 

7 

O 

46 

54 

3°= I 7 

5 6 


WNW 

1 

Fine. 


21 

O 

5 6 >5 

55=5 

3°=!3 

4 6 


wsw 

1 

Cloudy. 

14 

7 

O 

5 ° 

55 

30,06 

62 


svv 

1 

Cloudy. 


2 

O 

5 2 

56 

30,06 

63 


sw 

1 

Rain. 

15 

7 

O 

5 1 

55 - 5 - 

30,05 

6 7 

0,088 

sw 

1 

Cloudy. 


2 

O 

6 i =5 

58 

30,03 

5 1 


sw 

2 

Fair. 

16 

7 

O 

53 

57 

29,8 • 

64 

0,030 

sw 

1 

Fair. 


2 

O 

55 

58 

z 9=79 1 

61 


SSW 

1 

Rain. 


C 11 3 


METEOROLOGICAL JOURNAL 

for May, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather.- 

H. 

M. 

0 

0 

inches. 

Inches. 

Points. 

Str. 

May 17 

7 

O 

5 ° 

57-5 

29,70 

7 2 

0,546 

SSW 

2 

Rain. 


2 

O 

62 

59 

29,8c 

5 ° 


WSW 

2 

Fair. 

18 

7 

O 

55 

58 

2 9>77 

7 2 

0,044 

wsw 

2 

Cloudy. 


2 

O 

^3>5 

59’5 

29j90 

5 2 


w 

2 

Cloudy. 

l 9 

7 

O 

5 6 

59>5 

29,91 

6 1 

O 

O 

OO 

OO 

sw 

2 

Fair. 


2 

O 

66,5 

62 

29,92 

5 ° 


sw 

2 

Fine. 

20 

7 

O 

57 

6l 

30,04 

64 


sw 

I 

Cloudy. 


2 

O 

67 

6 3 

30,01 

5 2 


sw 

1 

Fair. 

2 1 

7 

O 

58 

62 

29,76 

69 

0,253 

SE 

1 

Cloudy. 


2 

O 

6l 

63 

29,84 

61 


w 

1 

Rain.. 

22 

7 

O 

53 

62 

3 °, 10 

62 

0,056 

w 

1 

Fair. 


2 

O 

61 

62,5 

30,11 

61 


w 

1 

Fair. 

2 3 

7 

O 

47 

60,5 

3°> 2 9 

58 

0,027 

NW 

1 

Fine. 


2 

O 

56,5 

61 

3°>3 1 

48 


NNE 

1 

F air. 

24 

7 

O 

48 

60 

30.39 

5 2 


E 

1 

Fine. 


2 

O 

56,5 

60 

30,36 

5 1 


E 

1 

Fine. 

2 5 

7 

O 

5 2 

59 

30,05 

59 


ESE 

1 

Cloudy. 


2 

O 

59 

60 

29,90 

5 1 


SSE 

1 

Cloudy. 

26 

7 

O 

53 

59 

/ 2 

68 

00 

ON 

O 

O 

WSW 

2 

Cloudy. 


2 

O 

63 

61 

2 9-73 

5» 


WSW 

2 

Fair. 

27 

7 

O 

53 

60 

29,76 

b 5 

0,1 14 

WSW 

2 

Fair. 


2 

O 

5 8 >5 

60 

29,62 

53 


S 

2 

Cloudy. 

28 

7 

O 

5 i -5 

59 

29,40 

62 

0,091 

WSW 

2 

Fair. 


2 

O 

55 

59 

2 9.37 

58 


s 

2 

Cloudy. 

2 9 

7 

O 

5 Z >5 

58 

29,32 

T>2 

0,064 

s 

2 

Cloudy. 


2 

O 

57 

59 

2 9*35 

56 


s 

2 

cloudy. 

'3° 

7 

O 

5 Z 

58,5 

29,62 

6 3 


ssw 

2 

Fine. 


2 

O 

62,5 

60,5 

29,60 

5-0 


SSW 

2 

Fair. 

3 1 

7 

O 

5 2 

59>5 

2 9.93 

64 


W 

1 

Fine. 


2 

O 

64 

61 

29,99 

46 


w 

1 

Fine. 


C 12 3 


METEOROLOGICAL JOURNAL 


for June, 1792. 


I 79 2 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

June 1 

7 

O 

53 

60,5 

3°-°7 

59 


s 

I 

Fine. 


2 

O 

6 7 

63 

30,02 

47 


ssw 

I 

Fine. 

2 

7 

O 

59 

61,5 

30,00 

67 


sw 

I 

Cloudy. 


2 

O 

66 

63»5 

3 °-i 8 

60 


N 

I 

Fine. 

3 

7 

O 

55 

6 l >5 

30,24 

62 


NNE 

I 

Cloudy. 


2 

O 

6 5>5 

63 

30,24 

48 


N£ 

2 

Fine. 

4 

7 

O 

53 

6 l ,5 

30,22 

59 


NE 

I 

Fair. 


2 

O 

°4 

64 

3 <M 7 

50 


N£ 

2 

.Fine. 

5 

7 

O 

50 

6l 

30,08 

65 


N 

2 

Cloudy. 


2 

O 

62 

62 

3°, 02 

57 


NNE 

I 

Fair. 

6 

7 

O 

51 

6l 

2 9-93 

59 


N 

I 

Cloudy. 


2 

O 

59-5 

61,5 

2 9>93 

5 ° 


NNE 

I 

Fair. 

7 

7 

O 

52 

6l 

29,91 

02 


NE 

I 

Cloudy. 


2 

O 

60 

6l 

29,87 

63 


NW 

I 

Fair. 

.8 

7 

O 

49 

60 

29,69 

66 

°-I 57 

SSE 

2 

Rain. 


2 

O 

57 

6l 

29,62 

59 


S 

2 

Cloudy. 

9 

7 

O 

5 i 

60 

29,78 

59 

0,053 

WNW 

I 

Cloudy. 


2 

O 

59-5 

6l 

29,76 

5 i 


S W 

l 

Cloudy. 

10 

7 

O 

53 

60 

29,65 

60 


SW 

I 

Cloudy. 


2 

O 

57-5 

6l 

29-55 

59 


ssw 

I 

Cloudy. 

1 1 

7 

O 

54 

60 

29,41 

6 5 

0,058 

w 

I 

Fair. 


2 

O 

61 

6l 

29,48 

61 


sw 

2 

Fair. 

12 

7 

O 

52 

60 

29,77 

58 

0,050 

wsw 

I 

Fine. 


2 

O 

59 

6l 

29,77 

53 


w 

I 

Cloudy. 

13 

7 

O 

52 

59-5 

29,72 

62 

0,015 

sw 

I 

Cloudy. 


2 

O 

53 

60 

29,66 

60 


SSE 

I 

Rain. 

H 

7 

O 

54 

59-5 

29,58 

69 

0,133 

WNW 

I 

Cloudy. 


2 

O 

59 

60,5 

29,85 

5 6 


NNW 

I 

Cloudy. 

15 

7 

O 

52 

60 

30,26 

60 


WNW 

I 

line. 


2 

O 

66 

61,5 

30,26 

40 


WNW 

I 

Fine. 

16 

7 

O 

58 

61,5 

30,27 

56 


E 

I 

Fine. 


2 

O 

67 

63.5 

30,26 

46 


E 

I 

Fine. 


n 13 3 


METEOROLOGICAL JOURNAL 

for June, 1792. 


1792 ' 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 
gro- 
in e- 
ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

June 17 

7 

O 

60 

62,5 

30,01 

57 


E 

1 

Fair. 


2 

O 

7 2 

65 

29,96 

49 


ssw 

1 

Fair. 

18 

7 

D 

55 

63»5 

29,97 

53 


WNW 

1 

Fine. 


2 

O 

6 3 

64 

29,92 

49 


WNVV 

1 

Fair. 

1 9 

7 

O 

55 

63 

2 9>74 

57 


NW 

1 

Fair. 


2 

O 

59 

63 

2 9>73 

55 


NW 

2 

Cloudy. 

20 

7 

O 

5 ° 

61,5 

2 9>73 

57 


NW 

1 

Cloudy. 


2 

O 

52,5 

62 

29,75 

66 


NW 

1 

Cloudy. 

21 

7 

O 

5 J >5 

60,5 

29,80 

To 

0,072 

NW 

1 

Cloudy. 


2 

O 

62 

6l 

29,80 

47 


NW 

1 

Cloudy. 

22 

7 

O 

53 

6l 

29,77 

59 


W 

2 

Fair. 


2 

O 

58,5 

6l 

29,75 

57 


sw 

1 

Cloudy. 

2 3 

7 

O 

5 1 

60 

29,8 1 

58 

0,174 

sw 

2 

Fair. 


2 

O 

59 

60,5 

29,80 

55 


sw 

2 

Cloudy. 

24 

7 

O 

53 

60,5 

29,88 

60 

0,051 

ssw 

2 

Cloudy. 


2 

O 

5 6 

60 

29,84 

60 


s 

2 

Rain. 

2 5 

7 

O 

5 2 

59>5 

30,04 

63 

QG 5 1 

w 

1 

Cloudy. 


2 

O 

6 3 

60,5 

30,14 

5 i 


WNW 

1 

Cloudy. 

26 

7 

O 

55 

60,5 

3 °A 7 

62 

0,039 

WNW 

2 

Cloudy. 


2 

O 

61,5 

61 

30,18 

56 


WNW 

2 

Cloudy. 

2 7 

7 

O 

57 

61 

30,18 

66 


SW 

1 

Cloudy. 


2 

O 

68 

62 

3 °,H 

59 


sw 

1 

Cloudy. 

28 

7 

O 

58 

62 

50,18 

6 5 


wsw 

1 

Fair. 


2 

O 

7 9*5 

64,5 

3°» , 5 

54 


wsw 

1 

Fair. 

2 9 

7 

O 

6 3 

64,5 

30,08 

64 


w 

1 

Cloudy. 


2 

O 

67 

6 5 

30,02 

64 


wsw 

1 

Rain. 

3 ° 

7 

O 

56 

64,5 

29,88 

64 

0,471 

WNW 

1 

Fine. 


2 

O 

63 

64,5 

29,92 

48 


WNW 

1 

Fair. 


c 


n j 4 3 


METEOROLOGICAL JOURNAL 

for July, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within.. 

Barom. 

Hy- 

gro- 

ne- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

July x 

7 

O 

54 

6 3>5 

29,99 

55 


WNW 

I 

Fair. 


2 

O 

63 

6 3>5 

29,99 

46 


NW 

I 

Fair. 

2 

7 

O 

54 

6 3>5 

30,00 

60 


WNW 

I 

Cloudy. 


2 

O 

64 

64 

30,00 

5 2 


WNW 

I 

Cloudy. 

3 

7 

O 

56,5 

6 3>5 

29,96 

57 


WNW 

I 

Cloudy. • 


2 

O 

60,5 

64 

29,91 

53 


WNW 

1 

Cloudy. 

4 

7 

O 

57 

6 3 

29,80 

67 


sw 

2 

Cloudy. 


2 

O 

64 

64 

29,80 

62 


sw 

I 

Cloudy. 

5 

7 

O 

57 

64 

29,95 

61 


w 

I 

Fair. 


2 ’ 

O 

59-5 

64 

29,85 

59 


sw 

2 . 

Cloudy. 

6 

7 

O 

57 

64 

30,00 

57 


WNW 

I 

Fair. 


2 

O 

60 

64 

30,02 

55 


WNW 

I 

Cloudy. 

7 

7 

O 

58 

64 

30,07 

67 


WNW 

I 

Cloudy. 


2 

O 

7 2 

65 

30,02 

56 


WSW 

I 

Fair. 

8 

7 

O 

58 

6 5 

29,94 

61 


SW 

2 

Cloudy. 


2 

O 

72 

6 5 

29,96 

54 


SW 

I 

Cloudy. 

9 

7 

O 

57 

65 

3 °, 01 

64 


SW 

I 

Cloudy. 


2 

O 

65 

65 

30,01 

61 


SSW 

I 

Cloudy. 

10 

7 

O 

61 

6 5 

2 9>93 

78 

0,296 

E 

I 

Cloudy. 


2 

O 

68 

66 

29,94 

63 


SE 

I 

Fair. 

1 1 

7 

O 

60 

6 5>5 

29,92 

76 

0,054 

NW 

X 

Cloudy. 


2 

O 

64 

66 

29,84 

75 


NNE 

I 

Cloudy. 

x 2 

7 

O 

57 

65 

29,60 

76 

O 

N 

00 

NNE 

I 

Cloudy. 


2 

O 

61 

65 

29,59 

74 


NNE 

I 

Cloudy. 

J 3 

7 

O 

57’5 

6 5 

29,68 

79 

0,067 

WNW 

I 

Rain. 


2 

O 

62 

64,5 

29,78 

76 


W 

I 

Cloudy. 

1 4 

7 

O 

58 

64 

30,03 

7 1 

0,048 

w - 

I 

Cloudy. 


2 

O 

69 

66 

30,10 

5 ° 


w 

I 

Cloudy. 

15 

7 

O 

60 

65 

30,19 

6 3 


w 

I 

Fair. 


2 

O 

75 -5 

66 

30,19 

5 ° 


w 

I 

Fair. 

16 

7 

O 

6 3 

6 5>5 

30,07 

59 


SW 

I 

Fine. 


2 

O 

76 

69 

29,96 

5 ° 


SSE 

I 

Fine. 




E is 3 


METEOROLOGICAL JOURNAL 
for July, 1792. 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. ■ 

Winds. 





without. 

within. 


gro- 











me- 




W eather. 

179Z 











H. 

M. 

0 

0 

Inches. 


Inches. 

Points. 

St r. 


July 17 

7 

O 

6 5 

67=5 

29,69 

69 

0,220 

SW 

2 

Cloudy. 


2 

O 

73 

68 

29,76 

51 


sw 

2 

Fair. 

18 

7 

O 

58 

67 

2 9>77 

69 


SW 

2 

Cloudy. 


2 

O 

7 i >5 

68 

29=79 

48 


sw 

2 

Fine. 

19 

7 

O 

60 

66 

2 9=93 

62 


sw 

2 

Fair. 


2 

O 

7 i .5 

67 

2 9=93 

49 


w 

2 

Fair. 

20 

7 

O 

58 

66 

29,95 

64 


w 

1 

Fair. 


2 

O 

6 7 

67 

29,87 

50 


E 

I 

Cloudy. 

21 

7 

O 

55 

65 

29,52 

80 

O 

tn 

O 

w 

2 

Cloudy. 


2 

O 

56 

64.5 

29,62 

79 


WNW 

1 

Rain. 

22 

7 

O 

54 

64 

2 9=97 

66 

0,601 

WNW 

1 

Fair. 


2 

O 

6 5 

64 

3°,°5 

60 


WNW 

1 

Fair. 

2 3 

7 

O 

55 

63 

3°=°5 

58 


WNW 

1 

Cloudy. 


2 

O 

6? 

64 

30,00 

49 


E 

1 

Cloudy. 

24 

7 

O 

53 

63 

2 9=95 

60 


E 

1 

Fair. 


2 

O 

68 

64 

29,92 

48 


E 

1 

Cloudy. 

2 5 

7 

O 

55 

63 

29,86 

64 


SE 

1 

Cloudy. 


2 

O 

60 

64 

2 9>77 

6 3 


SSE 

2 

Cloudy. 

26 

7 

O 

58 

63 

29,70 

68 

0,017 

SW 

1 

Fine. 


2 

O 

7*»5 

64,5 

29,70 

47 


sw 

1 

Fair. 

2 7 

7 

O 

58 

6 3=5 

29,58 

6 7 

0,06l 

sw 

2 

Cloudy. 


2 

O 

64,5 

64 

29,60 

53 


sw 

2 

Cloudy. 

28 

7 

O 

55 

6 3=5 

29,69 

61 


sw 

1 

Fine. 


2 

O 

7 1 

6 5 

29,71 

46 


sw 

1 

Fair. 

29 

7 

O 

57 

63=5 

29,61 

67 


ssw 

1 

Rain. 


2 

O 

60 

64 

29,52 

6 5 


E 

1 

Cloudy. 

3 ° 

7 

O 

55 

6 3 

29=87 

68 

0,26l 

N 

1 

Fair. 


2 

O 

69 

6 5 

29,96 

51 


NW 

1 

Fair. 

3 i 

n 

/ 

O 

55=5 

64 

30,10 

6 5 

0,036 

wsw 

2 

Cloudy. 


2 

O 

62 

64 

30,12 

6 3 


ssw 

2 

Cloudy. 


C ie 3 


METEOROLOGICAL JOURNAL 


for August, 1792. 


1752 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

0 

Inches. 

Inches. 

Points. 

Str. 

Aug. 1 

7 

O 

62 

64 

30,30 

68 


s 

I 

Cloudy. 


2 

O 

7 *» 5 

68 

30,26 

53 


E 

I 

Fine. 

2 

7 

O 

60 

66 

3°05 

73 


E 

I 

Cloudy. 


2 

O 

7 6 >5 

68,5 

30,08 

53 


E 

I 

Fine. 

3 

7 

O 

6? 

68 

30,00 

65 


E 

I 

Fine. 


2 

O 

76 

705 

29,96 

5 1 


E 

2 

Fine. 

4 

7 

O 

63 

69 

29,99 

64 


E 

I 

Fine. 


2 

O 

75 

705 

3°’°4 

5 ° 


E 

I 

Fine. 

5 

7 

O 

60 

69 

30,17 

64 


ENE 

I 

Cloudy. 


2 

O 

7 Z >5 

70,5 

30,12 

50 


NE 

Iv 

Fair. 

6 

7 

O 

62 

69 

3 0>1 1 

67 


ENE 

I 

Ciouay. 


2 

O 

73 

7 i 

30,06 

46 


E 

I 

Fine. 

7 

7 

O 

61 

69 

30,06 

61 


NE 

I 

Cloudy. 


2 

O 

72 

7 i 

3 °, u 

5 ° 


NE 

I 

Fine. 

8 

7 

O 

60 

69 

30,20 

68 


E 

] 

Cloudy. 


2 

O 

73 

70 

30,22 

53 


E 

I 

Fair. 

9 

7 

O 

60 

68 

30,20 

65 


E 

I 

Hazy. 


2 

O 

78 

72 

30,17 

49 


SSE 

2 

Hazy. 

10 

7 

O 

64 

69 

30, 18 

59 


SSE 

2 

Cloudy. 


2 

O 

79 

73 

3°A7 

46 


SSE 

1 

F iir. 

1 1 

7 

O 

6 3 

70 

30, 16 

60 


SSE 

I 

Fair. 


2 

O 

82 

73 

30, 11 

45 


SSW 

I 

Fine. 

12 

7 

c 

68 

70 

30,10 

53 


sw 

I 

Cloudy. 


2 

0 

84 

74 

3°>°5 

45 


sw 

I 

Hazy. 

13 

7 

0 

6 5 

72 

30,00 

62 


sw 

I 

Fine. 


2 

0 

78 

74 

2 9>97 

48 


sw 

I 

Fine. 

H 

7 

0 

6 5 

72 

29,98 

55 


w 

I 

Fair. 


2 

0 

75 

73 

29,98 

48 


WNW 

I 

Fair. 

15 

7 

0 

61 

7 i 

30,04 

53 


NW 

I 

Cloudy. 


2 

0 

71,5 

72 

30,04 

+8 


WNW 

1 

Fine. 

16 

7 

0 

61 

7 i 

29,85 

69 

0,031 

WNW 

I 

Cloudy. 


2 

0 

73 

1 7 1 

29,80 

5 6 


WNW 

I 

Cloudy. 


[ *7 3 


METEOROLOGICAL JOURNAL 


for August, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

W eather. 

H. 

M. 

O 

0 

Inches. 

Inches. 

Points. 

Str. 

Aug. 1 7 

7 

O 

60 

71 

29 80 

63 


W 

1 

Cloudy. 


2 

O 

73 

7 1 

29,79 

49 


w 

1 

Cioudy. 

18 

7 

O 

59 

70 

29,52 

80 

0,400 

NE 

1 

Rain. 


2 

O 

61 

69 

29,55 

7 6 


NE 

1 

Rain. 

19 

7 

O 

55 

68 

29,76 

69 

«-n 

00 

00 

O 

NNW 

1 

Fine. 


2 

O 

67 

68 

29,78 

5 1 


NW 

1 

Cloudy. 

20 

7 

O 

54 

66 

. 29-93 

65 


NW 

1 

Fair. 


2 

O 

65 

66 

29,90 

53 


NW 

1 

Cloudy. 

21 

7 

O 

5 6 

65 

29,59 

77 

0,440 

sw 

2 

Rain. 


2 

O 

70 

68 

29,53 

61 , 


sw 

2 

Fair. 

22 

7 

O 

57 

66 

29,47 

66 

0,041 

sw 

2 

Rain. 


2 

O 

68 

67 

2940 

53 


sw 

2 

Fair. 

23 

7 

O 

57 

6 5 

29,41 

6 3 


sw 

2 

Fair. 


2 

O 

67 

66 

29,47 

53 


w 

2 

Cloudy. 

24 

7 

O 

58 

65 

29,84 

68 

0,028 

w 

2 

Fair. 


2 

O 

70 

66 

29,94 

5 i 


w 

2 

Fair. 

2 5 

7 

O 

58 

6 5 

29-93 

67 

0,075 

sw 

2 

Rain. 


2 

O 

66,5 

66,5 

29,87 

61 


sw 

2 

Cloudy. 

26 

7 

O 

62 

66 

29,71 

72 


sw 

1 

Cloudy. 


2 

O 

64 

67 

29,60 

70 


SSE 

2 

Rain. 

27 

7 

O 

57 

66 

29,70 

6 3 

0,165 

wsw 

2 

Fine. 


2 

O 

69,5 

67 

29,80 

47 


wsw 

2 

Fine. 

28 

7 

O 

54 

6 5 

29,91 

66 


w 

1 

Fine. 


2 

O 

68,5 

67 

29,94 

47 


ENE 

1 

Fine. 

29 

7 

O 

57 

66 

30,12 

62 


NE 

1 

Cloudy. 


2 

O 

64 

65 5 

30,12 

55 


NE 

2 

Cloudy. 

3 ° 

7 

O 

58 

65 

29,95 

62 


NE 

1 

Cloudy. 


2 

O 

62 

65 

29,92 

66 


E 

1 

Cloudy. 

3 1 

7 

O 

57 

65 

30,00 

7 i 


E 

1 

Cloudy. 


2 

O 

68 

6 5-5 

29,98 

59 


ESE 

2 

Cloudy. 


£ 18 3 


METEOROLOGICAL JOURNAL 


for September, 1792. . 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

0 

O 

Inches. 

Inches. 

Points. 

Str. 

Sept. 1 

7 

O 

60 

65 

29,88 

69 

0,125 

SE 

1 

Cloudy. 


2 

O 

62 

65,5 

29,88 

68 


SSE 

1 

Cloudy. 

2 

7 

O 

59 

65 

29,90 

7 i 

0,068 

SSE 

I 

Fine. ' 


2 

O 

69 

66 

29,90 

55 


SSE 

2 

Fair. 

3 

7 

O 

57 

65 

29,81 

70 


SSE 

1 

Cloudy. 


2 

O 

66,5 

6 5>5 

29,77 

60 


SSW 

1 

Fair. 

4 

7 

O 

54 

64-5 

29,60 

67 

0,052 

WSW 

1 

Fair. 


2 

O 

67,5 

6 5 

29,60 

56 


sw 

1 

Cloudy. 

5 

7 

O 

49 

64 

2 9’74 

70 


sw 

1 

Foggy. 


2 

O 

66,5 

6 5 

29,84 

54 


WSW 

1 

Fair. 

6 

7 

O 

54 

6x 

3 °’ r 3 

70 


NNE 

1 

Foggy. 


2 

O 

67,5 

65 

3 °A 5 

58 


SSE 

1 

Fair. 

7 

7 

O 

57 

64 

3°44 

67 


WSW 

1 

Cloudy. 


2 

O 

6 5 

64,5 

30,08 

62 


WSW 

1 

Cloudy. 

8 

7 

O 

60 

64 

29,95 

7 2 


WSW 

1 

Cloudy. 


2 

O 

65 

6 5 

29,95 

61 


WSW 

1 

Cloudy. 

9 

7 

O 

53 

6 3 

30,00 

67 


NW 

1 

Cloudy. 


2 

O 

61 

64 

29,98 

58 


w 

i 

Cloudy. 

10 

7 

O 

60 

6 3>5 

29,70 

66 


WSW 

2 

Cloudy. 


2 

O 

65 

65 

29,76 

48 


WNW 

2 

Fair. 

1 1 

7 

O 

49 

6 3 

29,81 

62 


WNW 

2 

Fine. 


2 

O 

57 

63 

29,90 

57 


WNW 

1 

Fair. 

1 2 

7 

O 

49>5 

62 

30,08 

63 

0,030 

WNW 

1 

Cloudy. 


2 

O 

56 

62 

29,84 

6 7 


WSW 

2 

Rain. 

13 

7 

0 

53 

61 

29,62 

62 

0,172 

WSW 

2 

Fine. 


2 

O 

63 

6z 

29,70 

5 1 


WNW 

2 

Fair. 

H 

7 

O 

5 1 

61 

29,89 

68 


WNW 

1 

Cloudy. 


2 

O 

57 

6 1 

2 9’74 

74 


WNW 

1 

Rain. 

J 5 

7 

O 

45 

5 9’5 

3 o ,°3 

70 

°>493 

NW 

2 

Cloudy. 


2 

0 

53 

60 

30,19 

5 1 


NNW 

2 

Fine. 

16 

7 

O 

43 

59 

30,34 

64 


N 

1 

Fine. 


2 

O 

56,5 

5 9>5 

3°,34 

55 


WNW 

1 

Fine. 


t 19 3 


METEOROLOGICAL JOURNAL 

for September, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather.- 

H. 

M. 

0 

O 

Inches. 

Inches. 

Points. 

Str. 

Sep. 17 

7 

O 

48 

59 

3°» I 7 

61 


W 

1 

Cloudy. 


2 

O 

57 

59 

3 °A 1 

57 


ssw 

1 

Cloudy. 

18 

7 

O 

47 >5 

53 

3 ° ; °i 

7 1 

0,030 

ssw 

1 

Cloudy. 


2 

O 

60 

59 

29>95 

59 


ssw 

i 

Cloudy. 

J 9 

7 

O 

57 

59 

29,87 

74 


sw 

2 

Cloudy. . 


2 

O 

60 

60 

29,78 

67 


ssw 

2 

Cloudy. 

20 

7 

O 

48 

59 

29,52 

73 

0,213 

w 

1 

Fine. 


2 

O 

52 

59’5 

29,40 

65 


wsw 

2 

Rain. 

21 

7 

O 

43 

57>5 

29,38 

69 

0,280 

wsw 

2 

Fine. 


2 

O 

52 

58 

29,24 

6 3 


wsw 

2 

Rain. 

22 

7 

O 

44 

56,5 

29,09 

68 

0,072 

w 

2 

Fine. 


2 

O 

54 

58 

29,24 

60 


WNW 

2 

Rain. 

23 

7 

O 

42 

56 

29,47 

70 

0,043 

NW 

1 

Fine. 


2 

O 

53 

57 

29,57 

6 3 


WNW 

1 

Cloudy. 

2+ 

7 

O 

47 

55-5 

29,62 

69 

0,017 

w 

2 

Rain. 


2 

O 

54 

57 

29,45 

70 


S 

2 

Cloudy. 

25 

7 

0 

48 

5 5- -5 

2 9»33 

66 

0,014 

w 

2 

Cloudy. 


2 

O 

54 

5 6 

29,54 

6 5 


NW 

2 

Cloudy. 

26 

7 

O 

45 

55 

30,02 

70 

0,023 

WNW 

1 

Fine. 


2 

O 

56 

57 

30,06 

55 


NW 

1 

Fair. 

27 

7 

O 

47 

55>5 

30,07 

6 5 


NNW 

1 

Cloudy. 


2 

O 

57 

56,5 

30,00 

5 6 


NNW 

1 

Cloudy. 

28 

7 

O 

54 

56 

2973 

78 

0,040 

SW 

2 

Cloudy. 


2 

O 

56,5 

57 

29,58 

72 


ssw 

2 

Cloudy. 

29 

7 

O 

5 ° 

56,5 

29,47 

74 

0,071 

ssw 

1 

Fine, 


2 

O 

53 

57 

29,44 

70 


s 

2 

Rain. 

30 

7 

O 

5 6 

57>5 

29,40 

81 

0,167 

E 

1 

Cloudy. 


2 

O 

62 

58 

29,49 

6 7 


E 

1 

Cloudy. 


[ 2 ° 1 


METEOROLOGICAL JOURNAL 

for October, 1792. 


1792 

Time. 

Therm. 

without 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

ter. 

Inches. 

Points. 

Str. 

Oct. 1 

7 

O 

5 6 

58 

29,62 

78 

0,020 

E 

1 

Fair. 


2 

O 

6 3 

60 

29,63 

68 


E 

1 

Cloudy. 

2 

7 

O 

56 

59 

z 9>73 

80 

0,043 

ENE 

1 

Cloudy. 


2 

O 

57 

59>5 

29,70 

70 


NE 

1 

Cloudy. 

3 

7 

O 

53 

59 

29,80 

67 


ENE 

2 

Cloudy. 


2 

O 

5 2 

58 

29,83 

6 5 


ENE 

2 

Cloudy. 

4 

7 

O 

47 

57 

29,88 

64 


ENE 

1 

Cloudy. 


2 

O 

49 

56,5 

29,82 

62 


ENE 

1 

Cloudv. 

5 

7 

O 

47 

57 

29,74 

67 


E 

1 

Cloudy. 


2 

O 

5 ° 

58 

2 9’73 

6 3 


ENE 

1 

Cloudy. 

6 

J 

O 

49 

57 

29,71 

73 


ENE 

1 

Cloudy. 


2 

O 

5 2 

59 

29,72 

70 


NE 

2 

Cloudy. 

7 

7 

O 

48,5 

57 

29,78 

73 

0,028 

NNE 

1 

Cloudy. 


2 

O 

5 2 

59 

29,80 

6 3 


E 

1 

Cloudy. 

8 

7 

O 

47»5 

56,5 

29,85 

64 


NE 

1 

Cloudy. 


2 

O 

5 2 

58,5 

29,85 

59 


NE 

1 

Cloudy. 

9 

7 

O 

46,5 

5 6 >5 

29,80 

64 


NE 

1 

Cloudy. 


2 

O 

5 2 

58 

29,78 

60 


NNE 

1 

Cloudy. 

10 

7 

O 

46 

5 6 -5 

29,76 

77 

0,062 

N 

1 

Rain. 


2 

O 

49 

58 

29,76 

79 


N 

1 

Rain. 

1 i 

7 

O 

43 

57 

29,83 

74 

0,507 

N W 

1 

Fine. 


2 

O 

53 

58 

29,87 

62 


NW 

1 

Fair. 

1 2 

7 

O 

40 

5 6 

29,76 

73 


WNW 

1 

Cloudy. 


2 

O 

53 

58 

29,59 

62 


S 

2 

Cloudy. 

13 

7 

O 

44 

5 6 

29,46 

68 


SSW 

1 

Fair. 


2 

O 

54 

58 

29.39 

68 


SSE 

2 

Cloudy. 

14 

7 

O 

5 2 

5 6 >5 

29,26 

8! 

0.383 

S 

2 

Rain. 


2 

O 

52,5 

59 

29,29 

68 


sw 

2 

Cloudy. 

15 

7 

O 

5 2 

58 

29,38 

76 

0,168 

SSW 

2 

Rain. 


2 

O 

55 

59.5 

29,36 

69 


SSW 

2 

Cloudy. 

16 

7 

O 

48 

58 

29,68 

7 i 

°035 

sw 

1 

Cloudy. 

] 

2 

O 

53 

59 1 

29,63 

67 


sw 

2 

Cloudy. 


C 21 3 


METEOROLOGICAL JOURNAL 
for October, 1792 . 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 





1792 






me- 




XT T .1 






ter 






H. 

M. 

0 

O 

Inches. 


Inches. 

Points. 

Str. 


Oct. 1 7 

7 

O 

46 

58 

2 9-78 

73 

O 

0 

wsw 

I 

Fair, 


2 

O 

55 

60 

29,76 

67 


sw 

2 

Fair. 

18 

7 

O 

43 

58 

29,67 

69 


wsw 

2 

Fine. 


2 

O 

53 

60 

2 9,77 

58 


w 

1 

Fair. 

l 9 

7 

O 

39 

57 

2 9,95 

7 1 


w 

1 

Fair. 


2 

O 

5 ° 

58.5 

29,95 

58 


w 

1 

Hazy. 

20 

7 

O 

53 

58 

29,71 

77 


s 

2 

Cloudy. 


2 

O 

57 

59 

29,65 

72 


ssw 

2 

Cloudy. 

2 1 

7 

O 

5i 

58-5 

29-58 

81 

0,025 

s 

1 

Fine. 


2 

O 

56 

60 

29,54 

74 


SSE 

2 

Cloudy. 

22 

7 

O 

5 2 

59 

29,68 

76 

0,068 

SSE 

2 

Fair. 


2 

O 

58,5 

61,5 

29,78 

64 


SSW 

2 

Fair. 

2 3 

7 

O 

48 

59-5 

30,05 

7 i 


SSW 

2 

Fine. 


2 

O 

56,5 

61 

30,1 I 

66 

- 

SSW 

1 

Cloudy. 

24 

7 

O 

4 2 

59 

30,37 

68 


wsw 

1 

Cloudy. 


2 

O 

5i 

59-5 

30,42 

6 3 


NE 

1 

Cloudy. 

2 5 

7 

O 

42 

57-5 

30,32 

6 7 


NE 

1 

Cloudy. 


2 

O 

5 ° 

58-5 

30,30 

67 


NE 

1 

Cloudy. 

26 

7 

O 

44 

5 6 

30,12 

66 


ENE 

1 

Cloudy. 


2 

O 

47»5 

57-5 

30,00 

6 3 


E 

2 

Cloudy. 

2 7 

7 

O 

48 

5 6 

29-93 

74 


E 

1 

Cloudy. 


2 

O 

58 

59 

29,96 

71 


ESE 

1 

Cloudy. 

28 

7 

O 

54 

57-5 

29,90 

83 


SE 

1 

Cloudy. 


2 

O 

58 

60 

29,92 

73 


SSE 

1 

Fair. 

2 9 

7 

O 

5 2 

58 

29,90 

84 


W 

1 

Cloudy. 


2 

O 

58 

60 

29-93 

7 i 


W 

1 

Cloudy. 

3 ° 

7 

O 

48 

58 

29-95 

77 


W 

1 

Cloudy. 


2 

O 

54-5 

59-5 

29,82 

77 


SW 

2 

Cloudy. 

3i 

7 

O 

53 

59 

29,48 

80 

o-3 1 5 

WSW 

1 

Cloudy. 


2 

O 

57 

61 

29,61 

60 


W 

1 

Fair. 


d 


C 3 


METEOROLOGICAL JOURNAL 


for November, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

Nov. 1 

7 

0 

48 

59 

29,82 

70 

0,035 

w 

2 

Fair. 


2 

0 

52 

59’5 

29,75 

7 ° 


ssw 

2 

Cloudy. 

2 

7 

0 

42 

58 

30,00 

68 

0,080 

WNW 

I 

Fine. 


2 

O 

50,5 

61 

30,14 

63 


WNW 

I 

Fine. 

3 

7 

O 

59 

59 

30,19 

84 


W 

I 

Cloudy. 


2 

0 

58 

62 

30,20 

6 3 


SW 

I 

Fine. 

4 

7 

0 

47 

60 

30,16 

75 


SW 

I 

Fine. 


2 

0 

55 ’5 

6 3’5 

30’17 

69 


SSW 

1 

Fine. 

5 

7 

0 

42 

60 

30,22 

73 


ssw 

I 

Foggy. 


2 

O 

5 ° 

60,5 

30,25 

77 


ssw 

I 

Foggy. 

6 

7 

0 

39 

58 

30,25 

77 




Foggy. 


2 

0 

46 

59’5 

30,24 

79 




Foggy. 

7 

7 

O 

46 

58,5 

30,24 

75 


ssw 

I 

Cloudy. 

. 

2 

0 

49-5 

58,5 

30,27 

7 ° 


ssw 

I 

Cloudy. 

8 

7 

0 

49 

58,5 

30,41 

7 ° 


ssw 

I 

Cloudy. 


2 

O 

52 

59 

3°’44 

64 


ssw 

I 

Cloudy. 

9 

7 

O 

49 

59 

30,40 

67 


ssw 

I 

Cloudy. 


2 

O 

53 

59 

3°-32 

68 


ssw 

I 

Cloudy. 

30 

7 

0 

49’ 5 

58 

30-24 

7 1 


ssw 

I 

Cloudy. 


2 

O 

53 

59’5 

30,24 

66 


ssw 

I 

Cloudy. 

I 1 

7 

0 

49 

59 

30,22 

76 


ssw 

I 

Cloudy. 


2 

O 

50 

60 

30-17 

7 ° 


ssw 

I 

Cloudy. 

12 

7 

0 

42 

57 

29,92 

7 ° 


E 

I 

Cloudy. 


2 

O 

5 ° 

60 

29,78 

67 


ESE 

I 

Fine. 

*3 

7 

O 

48 

58 

29,47 

73 


E 

I 

Cloudy. 


2 

O 

52 

59’5 

29,44 

65 


S 

2 

Cloudy. 

H 

7 

O 

46 

57 

29,32 

71 

0,066 

s 

2 

Rain. 


2 

0 

52 

58,5 

29,36 

63 


ssw 

2 

Cloudy. 

IS 

7 

O 

44 

57-5 

29,64 

72 


wsw 

2 

Cloudy. 


2 

0 

49 

58 

z 9-73 

59 


w 

I 

Fair. 

16 

7 

O 

19 

56 

29.88 

66 


WNW 

I 

Fine. 


2 

0 

46 

57-5 

29,94 

64 


WNW 

I 

Fair. 


L 2 3 ] 


METEOROLOGICAL JOURNAL 
for November, 1792. 


Time. 

Therm. 

Therm. 

Barom. 

Hy- 

Rain. 

Winds. 





without. 

within. 


gro- 
in e- 




Weather. 

l 79 z 











H. 

M. 

O 

O 

Inches. 


Inches. 

Points. 

Str. 


Nov. 17 

7 

O 

34 

54-5 

3 °,i° 

6 7 


NW 

1 

Fine. 


2 

O 

40 

57 

3°, I 8 

6 3 


NW 

1 

Fine. 

18 

7 

O 

33 

53.5 

3°> z 7 

6 7 


NW 

I 

Fair. 


2 

O 

44 

5 6 -5 

3 °> l6 

6 5 


W 

1 

Cloudy. 

*9 

7 

O 

48 

54 

29,88 

67 


w 

1 

Cloudy. 


2 

O 

5 ° 

57 

2 9-95 

60 


w 

I 

Fair. 

20 

7 

O 

35 

55 

30,42 

64 


NW 

1 

Foggy. 


2 

O 

40 

55 

3°-43 

6 3 


WNW 

1 

Cloudy. 

21 

7 

O 

48 

54 

30,00 

78 


wsw 

2 

Cloudy. 


2 

O 

5 2 

55-5 

29,78 

73 


sw 

2 

Cloudy. 

22 

7 

O 

41 

54 

29,64 

68 

O 

OO 

Lki 

WNW 

1 

Fine. 


2 

O 

46 

5 5 » 5 

29,60 

6 3 


NW 

2 

Fine. 

23 

7 

O 

38 

54-5 

29,80 

66 


NNW 

2 

Fine. 


2 

O 

45 

55 

29,83 

68 


NNW 

2 

Cloudy. , 

24 

7 

O 

39 

54 

30,26 

72 

0,090 

NE 

1 

Cloudy. 


2 

O 

46 

57 

30,27 

66 


NE 

1 

Cloudy. 

2 5 

7 

O 

41 

53 

30,24 

6 S 


NE 

1 

Fine. 


2 

O 

47 

55-5 

3°- I 4 

66 


NE 

2 

Cloudy. 

26 

7 

O 

39 

53-5 

2 9-93 

70 


NE 

I 

Cloudy. 


2 

O 

43*5 

55-5 

29,84 

7 1 


NE 

1 

Cloudy. 

2 7 

7 

O 

42 

53 

29,83 

7 1 


NE 

1 

Cloudy. 


2 

O 

45 

54-5 

29,83 

66 


NE 

I 

Cloudy. 

28 

7 

O 

39 

53 

29,95 

7 2 


E 

1 

Foggy. 


2 

O 

4 1 

55 

29,92 

73 


E 

1 

Cloudy. 

2 9 

7 

O 

38 

5 2 

z 9 > 9 1 

68 


E 

1 

Fine. 


2 

O 

43 

54 

29,95 

66 


E 

1 

Fine. 

3 ° 

7 

O 

38 

5 2 

3°,°5 

7 2 


E 

1 

Cloudy. 


2 

O 

37*5 

53 

30,00 

70 


ESE 

1 

Cloudy. 


E M 3 


METEOROLOGICAL JOURNAL 

for December, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather. 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

Dec. 1 

8 

O 

34 

5 ° 

29,85 

70 


E 

I 

Cloudy. 


2 

O 

34 

5 1 

29,85 

69 


E 

I 

Cloudy. 

2 

8 

O 

37 

50 

30,15 

69 


E 

I 

Cloudy. 


2 

O 

38,5 

5 L 5 

3°)2I 

69 


NE 

I 

Cloudy. 

3 

8 

O 

37 

5 ° 

3°)35 

66 


E 

1 

Foggy. 


2 

O 

35 

5°)5 

3°’34 

66 


W 

I 

Cloudy. 

4 

8 

O 

37 

49)5 

30,26 

78 


WNW 

1 

Foggy. 


2 

O 

42 

5 i )5 

30,11 

80 


WSW 

I 

Cloudy. 

5 

8 

O 

5 2 

53 

29,60 

79 

0,152 

WSW 

I 

Cloudy. 


2 

O 

53 

55’5 

29,56 

77 


WSW 

1 

Cloudy. 

6 

8 

O 

43 

53-5 

29,64 

73 

0,041 

ssw 

I 

Cloudy. 


2 

O 

5°, 5 

56,5 

2 9’34 

7° 


sw 

2 

Cloudy. 

7 

8 

O 

3 8 >5 

5 3)5 

29,67 

62 

0,097 

WNW 

2 

Fair. 


2 

O 

39>5 

56 

29,92 

59 


NW 

2 

Fine. 

8 

8 

O 

3 2 

5 2 

30,25 

73 


NW 

1 

Fine. 


2 

O 

40 

55 

30,30 

66 


NW 

1 

Fine. 

9 

8 

O 

45 

53 

3 °,oq 

66 


W 

2 

Cloudy. 


2 

O 

49 

54-5 

2 9 , 9 1 

64 


W 

2 

Cloudy. 

10 

8 

6 

5 2 

55 

29,88 

7 2 


W 

2 

Cloudy. 


2 

0 

53 U 

57 

29,85 

68 


w 

2 

Cloudy. 

1 1 

8 

0 

44 

55 

30,00 

63 


w 

2 

Cloudy. 


2 

O 

45.5 

57 

30,00 

60 


WNW 

2 

Fair. 

1 2 

8 

0 

37 

54 

30,27 

62 


WNW 

1 

Fair. 


2 

0 

4 2 

55)5 

3 0 ,25 

63 


NW 

1 

Cloudy. 

13 

8 

0 

3 8 

53 

29,68 

78 

0,302 

ENE 

1 

Cloudy. 


2 

O 

39 

55 

29,72 

75 


NE 

1 

Cloudy. 

14 

8 

0 

49 

54 

29,76 

70 

0,162 

WNW 

1 

Cloudy. 


2 

0 

5 ° 

57 

29,80 

6 5 


WNW 

1 

Cloudy. 

>5 

8 

0 

45 

55 

2Q,QO 

68 


NW 

1 

Fair. 


2 

O 

49 

58 

2 9’93 

65 


NW 

1 

Fair. 

16 

8 

0 

39 

55 

30,22 

73 


ENE 

1 

Cloudy. 


2 

O 

43 

57 

30,24 

68 


ENE 

1 

Cloudy. 


t 2 5 3 


METEOROLOGICAL JOURNAL 


for December, 1792. 


1792 

Time. 

Therm. 

without. 

Therm. 

within. 

Barom. 

Hy- 

gro- 

me- 

ter. 

Rain. 

Winds. 

Weather,- 

H. 

M. 

O 

O 

Inches. 

Inches. 

Points. 

Str. 

Dec. 17 

8 

O 

42 

54 

3007 

78 


s 

1 

Cloudy. 


2 

O 

48 

57 

3°Oo 

73 


sw 

2 

Cloudy. 

18 

8 

O 

48 

5 6 

29,85 

76 


wsw 

2 

Cloudy. 


2 

O 

5M 

59 

29,82 

76 


w 

2 

Cloudy. 

l 9 

8 

O 

49 

57*5 

29,80 

67 


WNW 

2 

Fair. 


2 

O 

5 i 

59 

30,00 

58 


WNW 

2 

Fine. 

20 

8 

O 

5 2 

58 

2 9>73 

78 


SW 

2 

Cloudy. . 


2 

O 

53 

60 

29,64 

74 


w 

2 

Cloudy. 

21 

8 

O 

38 

5 6 

29,71 

66 

O 

O 

NW 

2 

Fine. 


2 

O 

43 

59 

29,87 

61 


NW 

2 

Fine. 

22 

8 

O 

45 

55 

29,58 

74 

0,051 

SW 

2 

Cloudy. 


2 

O 

45 

57 

29,22 

6 7 


sw 

2 

Fair. 

2 3 

8 

O 

34>5 

54 

29,45 

60 

0,095 

N 

2 

Fine. 


2 

O 

33 

56 

29,58 

55 


N 

2 

Fine. 

24 

8 

O 

3*»5 

5M 

29,78 

63 


NNW 

2 

Fair. 


2 

O 

34>5 

54 

29,79 

6 3 


NNW 

2 

Fair. 

2 5 

8 

O 

3 2 

5i 

29,54 

75 


NW 

j 

Foggy. 


2 

O 

38 

5 2 

29,51 

7 2 


WNW 

1 

Cloudy. 

26 

8 

O 

37 

5 i 

29,00 

77 

0,348 

WNW 

1 

Cloudy. 


2 

O 

36 

53 

29,00 

77 


WNW 

1 

Snow. 

2 7 

8 

O 

36 

5 i 

29,48 

77 

0,177 

WNW 

1 

Cloudy. 


2 

O 

39 

53 

29,56 

7 o 


NW 

1 

Cloudy. 

28 

8 

O 

36,5 

5 ° 

29,61 

72 

0,020 

NW 

1 

Fair. 


2 

0 

4 i 

53 

29,71 

67 


NW 

1 

Fine. 

2 9 

8 

O 

4 i 

Si 

29,88 

79 

C,10 3 

WSW 

1 

Cloudy. 


2 

O 

47 

53 

29,85 

81 


WSW 

1 

Cloudy. 

3° 

8 

O 

44 

5 2 

29,86 

77 

0,1 15 

W 

1 

Cloudy. 


2 

O 

45 

5 5 >5 

29,95 

68 


WNW 

1 

Fine. 

3 1 

8 

O 

3 2 >5 

5 i 

30.27 

72 


NW 

1 

Cloudy. 

i 

2 

O 

33’5 

54 

50,27 

73 


WNW 

1 

Hazy. 


L 26 ] 


1792. 

Thermometer 

without. 

Thermometer 

within. 

Barometer. 

Hygrometer. 

Rain. 

Greatest 

height. 

Least 

height. 

Mean 

height. 

Greatest] 

height. 

Least 

height. 

Mean 

height. 

Greatest 

height. 

Least 

height. 

Mean 

height. 

1 Greatest 
| height. 

| Least 
height. 

Mean 

height. 



Deg. 

Deg. 

Deg. 

Deg. 

Deg. 

Deg. 

Inches. 

Inches. 

Inches . 




Inches. 

January 

53 

l 9 

37 » 2 

57.5 

43 

51,1 

3°’47 

28,94 

29,66 




I,8lO 

February 

56 

1 6,5 

40,0 

60 

43 

52,6 

3°, 4° 

2 9’53 

29,98 




0,712 

March 

5 6 

26 

44>3 

6l 

46 

54 ’ 3 

30,51 

29,07 

2 9’77 

85 

48 

6 4>3 

079 1 

April 

66 

33 

52,0 

65,5 

54>5 

59’3 

3 °’ 3 2 

29,12 

29,90 

75 

44 

59 ’ 6 

055 ° 

May 

67 

42,5 

5 3>3 

6 3 

54 

58,2 

3°’39 

29,32 

z 9>97 

72 

43 

56,7 

1,624 

June 

79 > 5 

49 

58,1 

65 

59’5 

6 1 ,6 

30,27 

29,41 

2 9»93 

67 

40 

5 7’7 

On 

July 

76 

53 

61,7 

69 

63 

64,8 

30,19 

29,52 

29,88 

80 

46 

60,9 

2,299 

August 

84 

54 

65,7 

74 

64 

68,5 

3 °> 3 ° 

29,40 

2 9>93 

80 

45 

59 ’ 1 

2,065 

September 

69 

4 2 

55 ’ 1 

65,5 

55 

ON 

O 

3°»34 

29,09 

2 9>79 

81 

48 

60,5 

1,91° 

October 

63 

39 

51,0 

61,5 

5 6 

5 8 >3 

30,42 

29,26 

2 9>79 

84 

58 

69,8 

1,884 

November 

53 

35 

45 ’5 

6 3>5 

5 2 

56,9 

30, 44 

29,32 

30,02 

84 

59 

68,9 

°,454 

December 

53 

3 1 »5 

409 

60 

49’ 5 

54 > 2 

3°’35 

29,00 

29,85 

81 

58 

69,9 

1,766 

Whole year 



5°’ 5 



58,4 



29,87 




19,489 


PHILOSOPHICAL 


TRANSACTIONS 

OF THE 

ROYAL SOCIETY 

OF 

LONDON. 

FOR THE YEAR MDCCXCIII. 
PART II. 

LONDON, 


SOLD BY PETER ELMSLY, 
PRINTER TO THE ROYAL SOCIETY. 
MDCCXCIII. 










' 










* 


. 


























' 




. 












• \ 













CONTENTS. 


XII. A Description of a Transit Circle, for determining the 

Place of celestial Objects as they pass the Meridian. By the 
Rev. Francis Wollaston, LL. B. and F. R. S. p. 133 

XIII. Description of an extraordinary Production of Human 
Generation, with Observations. By John Clarke, M. D. 
Communicated by Sir Joseph Banks, Bart. P. R. S. p. 154 

XIV. Description of an Instrument for ascertaining the specific 

Gravities of Fluids. By John Godfrey Schmeisser. Commu- 
nicated by Sir Joseph Banks, Bart. P. R. S. p. 1 64 

XV. Extract of a Letter from Sir Charles Blagden, Knt. 

Sec. R. S. to Sir Joseph Banks, Bart. P. R. S. giving some 
Account of the Tides at Naples. p. 168 

XVI. Observations on Vision. By Thomas Young. Communi- 
cated by Richard Brocklesby, M.D. F. R. S. p. 169 

XVII. Observations on a Current that often prevails to the 

Westward of Scilly ; endangering the Safety of Ships that 
approach the British Channel. By James Rennell, Esq. 
F K S. p. 182 

XVIII. Observations on the Planet Venus. By William 
Herschel, LL. D. F. R. S. p. 201 


C iv 3 

XIX. Abstract of a Register of the Barometer, Thermometer , 
and Rain, at Lyndon, in Rutland. By Thomas Barker, Esq.', 
witj> the Rain in Surrey and Hampshire, for the Tear 1792 ; 
and a Comparison of wet Seasons. Communicated by Thomas 
White, Esq. F. R. S. - 220 

Presents received by the Royal Society, from November 1792, 
to June 1793. p. 229 

Index. p. 233 


PHILOSOPHICAL 


TRANSACTIONS. 


XII. A Description of a Transit Circle, for determining the 
Place of celestial Objects as they pass the Meridian. By the 
Rev. Francis Wollaston, LL. B. and F. R. & 


Read May 9, 1793. 

An instrument which, in one observation, is capable of giving 
with precision both the right ascension and declination of 
celestial objects, has always appeared to me one of the desi- 
derata in astronomy. Though I had often considered the va- 
rious methods practiced for ascertaining each, and turned it 
in my mind how I could contrive to make one instrument 
answer both purposes ; I never could satisfy myself in what 
way to effect the one. without destroying the accuracy of the 
other ; till one evening, at a meeting of our Society in the 
beginning of 1787, Mr. Ramsden mentioned to me his idea of 
reading off the divisions of an instrument, by a microscope 
having a micrometer in the field of view, which, being de- 
tached from the limb, could examine with accuracy the 
MDCCXC III. T 


134 Mr. Wollaston's Description 

distance of the nearest division from a fixed point. It occurred 
to me immediately, that this was the thing I wanted : be- 
cause a circle attached to the telescope of a transit instru- 
ment, and passing in review before such a microscope, or a 
pair of such microscopes, would answer the purpose. I did 
not then know, that a microscope of that kind had been ap- 
plied by the late Due de Chaulnes, to his dividing engine, 
for determining the divisions ; described minutely by him, 
and published in 1768 ; a copy of which is in our library. 
Neither did I then know of the same idea having been the 
foundation of Roemer's method of reading off the divisions 
on his Circulus meridionalis ; an account of which was pub- 
lished by Horrebow, in the beginning of this century ; 
where a reticule of ten squares was made, by trials of its 
distance from the limb of the instrument, to coincide with a 
division of ten minutes on that limb. With them I was not 
acquainted, till after my instrument was already in some for- 
wardness. Whether Mr. Ramsden took the first hint from 
either of them, and improved upon it, I cannot say. He has 
brought it into use among us : I certainly derived it from 
him ; and to him I acknowledge myself indebted for it. 

This method of reading off’ has, indeed, been applied al- 
ready with great success to different instruments ; but I do 
not know that it has ever yet been adapted to the transit. 
Circles of various kinds have been constructed with wonder- 
ful accuracy, yet all have been formed with another view; 
and their turning freely in azimuth, seemed to render them 
less fit for the purpose which I wanted ; i. e. a circle, firmly 
fixed, and turning truly in the plane of the meridian by 
means of a transverse axis ; with all the adjustments of a 


«35 


of a Transit Circle. 

transit at the end of the axis itself (which appear to me es- 
sential to a due performance) ; and at the same time with the 
opposite readings, and all the adjustments of the circles now 
in use. 

On this idea the following instrument was constructed: 
and since there are some particular contrivances in it, which 
are new, I take the liberty of laying a general description of 
it before this Society ; not by way of setting forth the praises 
of any one instrument; but that this may be known in all its 
parts, with the advantages and disadvantages of each, as far as 
I have discovered any ; and that such of them as are judged 
useful, (if the Committee shall think proper to honour this 
paper with a place in our Transactions) may be adopted by 
others. 

My first design was, not to have given orders for one my- 
self, but merely to communicate the thought to those who 
might improve upon it. Accordingly, I mentioned it first to 
Mr. Ramsden, in 1788 : but the multiplicity of his engage- 
ments, and the fertility of his own imagination, (at that time 
particularly turned towards contriving to make instruments 
move freely in azimuth) rendered him disinclined to listen to 
a scheme for one on another plan. The same was the case 
with Mr. Troughton. I mentioned it likewise to several of 
my acquaintance: but (perhaps the trouble and expense at- 
tending the construction of a first instrument, seldom so com- 
plete as a second or a third of the kind, might be the cause) 
no one was set about. After three years waiting, and be- 
coming, in the mean time, more and more convinced of the 
advantages of such an instrument to astronomy ; and Mr. 
Cary being recommended to me, as fully qualified for the 

T 2 


136 Mr. Wollaston's Description 

purpose ; though I am growing too old to expect to make 
many more observations, I gave orders for one of a size and 
form which I thought most convenient to myself. Observers 
know best what it is they want ; and an instrument-maker 
who will condescend to listen to them, is a treasure. In this, 
as well as other respects, it is but justice to Mr. Cary to say, 
that he has answered the character which was given of him. 
He has shewn himself, during the whole time, very diligent 
and attentive ; comprehending readily my directions ; giving 
freely his opinion, and his reasons for dissent, if he disap- 
proved of what was proposed ; yet being willing to follow 
mine, if I still continued in the same mind ; improving upon 
some of my hints ; and executing in a masterly way every 
part of it. 

The drawing accompanying this paper (Tab. XV.) will 
shew the general form of the instrument ; and need very 
little explanation. 

The whole stands on three feet, adjustable by screws. The 
bottom plate (of 21^ inches diameter) turns in azimuth ; not 
on a long axis, but on a center ; and rides on a bell-metal 
circle, truly turned, and to which the bottom plate itself is 
ground. In this way it moves very smooth by hand ; but it 
is capable of being turned by a winch, with tooth and 
pinion. The intent of its turning thus, is merely for the 
convenience of reversing the instrument : for, though it 
might be used out of the meridian, and for azimuths ; yet, 
since it is designed principally for meridian passages, when it 
is in its place the whole is clamped firmly to the bottom 
frame by four clamps, which confine it to the circle on which 
it rides : and this method of turning proves itself to be 


1 37 


of a Transit Circle . 

steady, by the levels on the bottom plate never altering in the 
least upon screwing the clamps. 

The four pillars, and their braces, explain themselves. 
They stand over the bell-metal circle ; and the clamps are 
placed near the foot of each, for greater steadiness ; since 
they carry the Y s for the pivots of the transit. 

The construction of these Ys is peculiar : they hang, as it were, 
in gimmals, though of a very firm kind, a drawing of which 
(Tab. XVI. fig. 1) will best explain them. They have a hori- 
zontal motion, smooth and steady : the T, or frame, AB, which 
carries them, turning on a perpendicular axis of 2^ inches, CD, 
ground to its socket; on the outside of the plate EF, which 
connects them with the pillars, and resting on that plate, to 
which the bottom of the frame itself is ground likewise. In 
this frame they have a vertical motion : the Ys themselves 
carrying a horizontal axis at AB, which, consisting of two 
frusta of cones on each side, in contrary directions, with a 
collar over them, guards against any shake whatsoever, while 
it admits of the Y adapting itself to the direction of the pivot. 
The idea of hanging them in this way, as well as that of 
turning the whole instrument in azimuth on a ground plate, 
was suggested by our late member Mr. John Smeaton ; to 
whom the world has, during many years, been indebted for re- 
peated capital improvements in mechanics. 

By thus hanging the Ys, the pivots have a bearing on them 
from end to end ; instead of riding on a bell-metal ridge, as 
is the usual method where the. Ys are fixed, and cannot set 
themselves in the direction of the axis. This seems to be a 
better bearing, and much less likely to wear the pivots. 

Yet, to guard against any wear, a pair of cylindrical 


138 Mr . Wollaston's Description 

springs, included in a tube, are applied through rings within 
the connecting plate above mentioned. These carry, each of 
them, a pair of rollers, on which a brass collar at each end of 
the axis of the telescope rides. The springs may be used or 
removed, at pleasure ; and they can be strengthened or 
weakened, by means of a screw at the bottom of the tube, so 
as to take off from the pivots any part of the weight that ma}’ - 
be judged best : and, since they are in a line with the axis, 
and are made capable of obeying it in every direction, there 
is no danger of their deranging its adjustments, while they 
render its motion exceedingly light and smooth indeed. 

The adjustments of the Y s are both of them at the same 
end of the axis, opposite to the divided circle and the micro- 
scopes ; because the smallest adjustment of that end of the 
axis between the microscopes, would have affected them so as 
to require an entire re-adjustment of them too. At the farther 
end, the axis is perforated, to admit light for illuminating 
the wires. And I find that (to my sight at least) it is much 
most agreeable to close the aperture with a pale green glass. 
The axis itself is 18 inches long, exclusive of the pivots, 
which are about each. 

The microscopes need no description. They are on the 
same principle as those described by our late member Major 
General Roy. (Phil. Trans. Vol. LXXX, p. 145 ) Mine are 
9 inches long ; the object-end at 2 inches from the limb of 
the circle. They magnify 24 times. One revolution of the 
micrometer-screw is equal to one minute ; and the head is 
divided to seconds. 

The fixed or stationary wire in them, is at the first notch, 
or minute itself ; and it is adjusted by means of a plumb-line. 


of a Transit Circle. 139 

which hangs from the top plate, and passes by the side of the 
axis; at about 8 degrees, or 1 inch from the centre. For 
this purpose there are dots made on the limb, at a suitable 
distance on each side of the zero, both above and below, 
whether the telescope be horizontal or perpendicular either 
way. These are viewed through two compound microscopes, 
(of inches long, and their object-glass at 3 inches distance 
from the limb) carried by the same frames as the other mi- 
croscopes. 

The cursor, or moveable wire, in tl?e micrometer-micro- 
scopes, is adjusted much in the same way as General Roy's ; 
excepting that the micrometer head is made to turn stiffly on 
the neck of the screw, so as to allow of bringing the point of 
zero to front the eye, without the trouble of re-adjustment, if 
it happened to fall behind. 

It may be asked, since I use a compound microscope for 
viewing the wire, why I choose a plain plumb-line close to 
the limb, in preference to one in the combined focus of the 
glasses l My reason is this ; I use a compound microscope, 
because my eyes do never, with any comfort, adapt them- 
selves to a single magnifier ; and in this way I have more 
light, and can keep my eye at a greater distance. I approve 
much of Mr. Ramsden's ghost, as it is called, where it can be 
used with safety. But in this instrument, I thought I could 
not confide in it, as the microscope must be on a different 
support : whereas the looking at the dot itself, and the wire 
together, through a tube of above 5 inches, and at a distance 
of 10 or 12 from the limb, could admit of little or no parallax. 
I had intended making use of the original dots of the di- 
visions for this purpose ; but they are so minute, that the 


140 Mr. Wollaston's Description 

smallest wire capable of supporting a plummet eclipses them 
entirely. 

There is of course a level (and a very sensible one it is) 
for adjusting the axis. The circle was ordered to have ten 
radii 4 that when the telescope is horizontal, and pointing to 
a meridian mark, there might be a vacancy between the cones, 
above or below, for introducing a level. In the brace be- 
tween the pillars, over the moveable Y, (at A, Tab. XV. ) it may 
be observed, the bottom bar is omitted ; in order to give the 
better room for passing the level, without inclining it, or run- 
ning any hazard of striking it. From the lower bar of the 
opposite brace B, over the fixed Y, there stands out a forked 
piece of brass, to receive the leg of the level, and direct it to 
its place ; as also for keeping it upright when the foot stands 
on the pivot, and just allowing a very little shake, so as not 
to cramp it. By this contrivance the level is easily handled, 
and reversed, without danger of disturbing it or the instru- 
ment. 

The top plate, as may be seen in the drawing, has a large 
opening cut more than half way across it. The design of this 
is, to allow you to observe quite up to the zenith, and a little 
beyond it, clear of all obstruction whatsoever. And since 
the whole instrument is capable of being reversed, or turned 
half way round in azimuth ; when you have occasion to ob- 
serve the transit of stars, in that part of the heavens where 
they would be intercepted by the plate in one position, it 
is entirely out of the way in the other. 

The circle itself is of full two feet diameter at the divi- 
sions ; being 254 inches at the edge. The undivided circle, 
on the side of the telescope next to the open end of the axis, 




of a Transit Circle . 

serves for strength and uniformity ; and to it is applied the 
clamp for elevation. That clamp is so made, as to allow the 
circle to run freely all round if you please ; not bearing at 
all against it, but supporting itself, and yet being easily re- 
moveable. It has no command over the circle whatever, 
when handled with care, excepting in the altitude of the te- 
lescope, by an adjusting screw when the clamp is set : and, 
as that screw has a milled head at each end, it is as conve- 
niently turned from the one as from the other side of the in- 
strument, to bring the horizontal wire to bisect the object. 

The telescope is of 2 inches aperture, and 33 focal length. 
The object-glass does not slide within the tube ; but screws 
into the end of a piece of false tube, of 4 inches length, which 
slides on the outside of the principal tube, and is fixed in its 
place, by 3 screws and collars running in grooves, when 
its distance from the wires is adjusted. In this way, one has 
the whole aperture of the tube ; and no greater length than 
is absolutely necessary for use ; which, in such an instrument, 
appeared to me to be an advantage. In some respects I find 
it so : yet, the hazard of disturbing the collimation, by touch- 
ing the outside of the tube, is an objection. 

The wires are not in one cell ; but in two distinct cells, with 
their faces towards eacli other. The perpendicular wires are 
5, at 35 seconds of time distance in the equator; and are ad- 
justable horizontally for collimation by a screw. The hori- 
zontal wires are 3, at about 1 5 minutes of a degree asunder ; 
placed so as just not to touch, but to pass clear of the other 
wires ; and they are adjustable in collimation by another 
screw peculiar to them. The two cells have each a power of 

MDCCXCIII. U 


Mr. Wollaston's Description 

turning separately on the axis of vision ; but, when once the 
two sets of wires are brought to be truly at right angles to 
each other, the cells can then be fixed together, and turned 
together, and finally settled in their place by screws and col- 
lars at the outside of the tube. These things, I believe, are 
new : I thought they might be improvements on the usual 
method ; yet I find the adjustment of the horizontal wires in 
collimation, might be dispensed with. 

My reason for having 3 horizontal wires, and at about that 
distance, was, that after having ascertained what the dif- 
ference is, I might observe the lower limb of the sun or moon 
at the one, and the upper limb at the other of the extreme 
wires, without much altering the elevation of the telescope, and 
removing the centre of the object, or preceding and subsequent 
limbs of the sun or moon, far out of the centre of the field. 

The divisions on the circle itself come now to be spoken to. 
They were done by hand ; and have been executed with 
great care. The original divisions are by dots or points, at 
every ten minutes. Within, is another row, by strokes or cuts ; 
laid off from the points to every ten minutes likewise. The 
dots are what we will regard first : the cuts afterwards. 

As it always appears to me convenient, in actual observa- 
tion, to contrive that every thing shall do itself, as far as I 
can, and to leave the mind as well as the body at perfect 
ease, and totally disengaged from calculation ; I considered, 
that making both the microscopes talk the same language, 
read off the same way, with the guiding figure always to the 
same hand, and the dot to be observed to the same hand too, 
and the readings always positive, would conduce much to 


of a Transit Circle . 143 

one’s ease, and thereby very greatly indeed to the accuracy 
and certainty of the observation. 

With this intent, since the microscopes are, the one above, 
I ordered that to be marked A ; the other below, B ; consi- 
dering that the numbers deduced from them could never be 
mistaken, if one got into the habit of examining A first, and 
noting that down, and then examining and setting B under 
it ; which, if all things are true, ought to be the complement 
to 90 degrees. 

To make the reading pleasant, I ordered the micrometer- 
screw in each to be placed on the right hand ; and considered 
the moveable wire as always to be kept to the right hand of the 
other. This will of course, in all cases, measure the distance 
of the fixed wire from the nearest dot apparently on the right, 
(or, since the microscopes invert, the nearest dot really to the 
left) which will be either the degree itself on that hand, or 
some multiple of ten minutes from it. 

That the numbering of the degrees might coincide with 
this idea, I considered, that the figures should be made to ap- 
pear erect in the microscopes, in every position of the tele- 
scope (which they might be whenever it does not point be- 
low the horizon) and that they should be reckoned back- 
wards. To effect this, they ought to be reckoned backwards 
in themselves, but to stand the contrary way, or inverted 
in reality. This would be different in the two microscopes, in 
respect of the centre of the circle ; but that could create no 
difficulty. For, since the two quadrants nearest to the object- 
end of the telescope, would always be those coming under 
the examination of microscope A ; and the two nearest to the 
eye-end, those to be observed at microscope B ; they might be 

U a 


144 Mr. Wollaston^s Description 

figured accordingly. Hence, supposing the instrument placed 
in the meridian, with the graduated face turned towards the 
east ; if, when the telescope is horizontal and points to the 
south, the upper quadrant nearest to the object-end, be num- 
bered from that end from 1 to go°, with the heads of the fi- 
gures towards the centre of the instrument ; and the other 
upper quadrant be numbered from the eye-end, with the feet 
of the figures towards the centre ; they both would give the 
zenith distances of the objects observed. The former, at mi- 
croscope A, while the telescope points to the south of the 
zenith ; the latter at microscope B, when you are observing 
towards the north. 

The two other, or lower quadrants, follow a similar rule, 
and serve to shew the altitudes, if botli be numbered from the 
quadrature, instead of either end of the telescope ; those lead- 
ing towards the object-end, being placed with their heads, 
while those towards the eye-end, stand with their feet to- 
wards the centre of the circle. 

To render this more intelligible, I will annex a drawing of 
the divisions, (Tab. XVI. fig. 2) numbered indeed only to every 
ten degrees ; though the instrument itself has a figure at every 
degree, that one may always be in the field of view of the 
microscope. Hereby it may be seen, that all on one side of 
the telescope give zenith distances, while all on the other side 
give altitudes ; and yet, that the figures in both the quadrants 
nearest to the object-end are placed with their heads towards 
the centre, and all towards the eye- end with their feet. This 
became necessary ; and though it was a little perplexing at 
first to contrive, and see executed properly, it is found very 
convenient indeed in use. 


of a Transit Circle. 145 

The interior divisions, or cuts, are also numbered at every 
degree each way, from the eye-end to the object-end of the 
telescope, with the feet of the figures always towards the 
centre. The use of them is likewise very great ; not for read- 
ing off the observations, but for setting the instrument. For, 
at a proper distance from the main pillars, there is a small 
pillar, carrying a compound microscope with a wire in its fo- 
cus ; which being adjustable, and once set to the latitude of 
the place, gives immediately the north polar distance of any 
object seen ; or, by fixing the instrument according to the 
polar distance of an object sought, one is certain of its enter- 
ing, at the proper time, the field of the telescope, near the 
centre wire. This pillar for the polar microscope, is remove- 
able to the other side of the main pillars ; which becomes ne- 
cessary when the instrument is reversed. 

This in general is the form, and these are the peculiarities 
in the construction of this instrument ; which, being de- 
signed for meridian observations, or transits, I apprehend may 
best be named a Transit Circle. 

In the progress of it, when the divisions came to be exa- 
mined in their proper position, as to the truth of the opposite 
dots being exactly in the diameter of the circle, an error was 
discovered, which occasioned a great deal of trouble, and 
much loss of time. When the microscopes had been adjusted 
with care, after turning the circle one way, they continued 
true, and the same dots shewed themselves to be perfectly in the 
diameter, however often the circle were turned the same way 
round : but on one or more revolutions the contrary way, the 
same dots ceased to appear true. This, it was thought, could 
arise only from some deviation in the centre. And, since the 


14® Mr. Wollaston's Description 

Ys hanging in gimmals was a new experiment, this error was 
supposed to take its rise from some shake in them. They 
were examined; and were altered in various ways. Fixed Y s 
were then made, of the usual form ; others of a larger ; others 
of a more acute angle. The difficulty was still thought to 
continue. Recourse was then had to Y^ in gimmals again, 
which I was unwilling to give up ; and friction-rollers were 
applied to take off some of the weight. Still this error did 
continue in a small degree : yet was that degree so small, as 
not to be discernible at the polar microscope ; nor, as far as I 
could see, at those belonging to the plumb-line ; and some- 
times scarcely so at the others, to whose greater magnifying 
power it seemed to be owing that it was at all perceptible. 
The cause I then supposed to be, in a disposition in the pi- 
vots to gather up the side of the Ys towards which they 
were turned. Yet was that not the cause : for what little mo- 
tion there was, I found afterwards to be in a contrary di- 
rection. 

This led me into discovering, and at last rectifying the de- 
fect. The original idea of hanging the Y s in gimmals, as was 
said before, was derived from Mr. Smeaton; who kindly 
shewed to Mr. Cary those which he had made to a small 
transit instrument for his own use. His ought scarcely, in 
strictness, to be called Ys ; for he had made a little hollow 
on each side where the pivots would touch, as a sort of bed 
to receive them, and make the angle less pinching. This, 
Mr. Cary had imitated : and, though I did not mean he 
should, he did the same to the second pair he made, after 
trying the other kinds. Since it was done, I let them so re- 
main till I got the instrument home ; for I really found all 


H 7 


of a Transit Circle. 

trials so disturbed by the shaking of carriages, while it was 
at his house, that I could make no satisfactory examination 
there myself. When the instrument was in its place, I tried 
every experiment I could contrive to discover the cause of 
this error; whether it could be in the microscopes themselves; 
any shake in them, or in the pillars, or in the hanging of the 
Ys. Finding none of these to be in fault ; and, upon trying 
the instrument at every 10 degrees all round, perceiving the 
axis thrown backward instead of forward upon turning either 
way, it occurred to me, that any grease or other particles 
would have it more in their power to produce that effect in a 
sort of pivot-hole, (which the hollowed sides really are) 
than between two fair flat surfaces. I thereupon took out the 
Y s, and had them formed to an exact right-angle, with the 
whole sides perfectly smooth, and flat, and well finished : 
and, since that has been done, I ready can discover no dif- 
ference which ever way the circle be turned ; but think I may 
now say that deviation is quite removed. 

Yet, I apprehend, it would have been of no consequence if 
it had continued, or been greater than it was. For, since the 
readings are as it were in a line above and below the centre, 
and both of them positive ; any motion of the centre towards 
the right hand, would give the dots, both above and below, 
the appearance of being more to the left than they ought to 
be ; and thence would give the measurement too small, and 
that in an equal degree in each ; so that the sum of zenith 
distance given by one microscope, and of altitude by the 
other, would thereby be less than go degrees, by just double 
the error. And if the axis be moved towards the left, the 
contrary would be the result ; the sum would exceed go de- 


$4$ Mr. Wollaston's Description 

grees, by just double that quantity. Hence, the difference 
from go degrees, at the same time that it gives a mean be- 
tween the two readings, would reduce the error or deviation 
of the axis to nothing. 

The instrument here described, is of the size I thought 
would be most convenient for my own use : indeed it is full 
as large as I should recommend ever to be made in that 
moveable form. It stands on a cylinder of one sofd stone, of 
2,y§- inches diameter, and 3 feet 6 inches long, bedded on a 
pier of brick, well bonded together, and rising from a good 
foundation, deep in the earth. The stone is clear of the floor 
all round, and is very steady indeed : the instrument rarely 
varies at all, in any respect. It is adjusted in the meridian 
to two marks, the one north, the other south ; so that now 
they are truly placed, the collimation of the telescope is 
easily examined, without lifting the circle out of its Ys. 

I may be supposed partial to an idea which I have long 
entertained ; but I confess, I should very strongly recom- 
mend the having an instrument of this nature, though more 
perfect, in every observatory ; I mean a transit instrument, 
on stone piers, with a suitable circle and microscopes ; that, 
whenever you observe a meridian passage, you may, at the 
same time, measure the exact altitude, or zenith distance of 
every object seen. The being obliged, in the common way, 
to have recourse to two different instruments, occasions the 
zenith distances to be much less frequently observed, than it 
is to be wished they were. It is true the British catalogue 
was, for the most part, deduced from observations with a 
quadrant alone ; and so was Mayer's. But, though labour 
and patient perseverance, may enable an observer to allow for 


of a Transit Circle. 149 

any deviations in the limb, a quadrant is at the best but an 
imperfect instrument for right ascensions. 

I believe, in the best observatory, I should confine myself 
to a telescope of 4,5 inches, with a circle of about 3 feet 6 
inches. Such a telescope would have great power ; and the 
whole would not be encumbered with too great weight. If 
the telescope be of 5 feet, the circle must be of 4 feet 6 inches 
But I certainly should dissuade the ever going beyond that ; 
and I doubt whether the great additional weight of metal, 
and the disparities there will be in such a mass, would not 
counteract the advantage of a longer telescope. Beside, it 
may deserve consideration, that in a larger instrument some 
parts may be out of the extent of the observer's arms, which 
he could wish to reach. Our late friend, Mr. Smeaton, was 
against a circle of above 3 feet diameter. Between stone piers, 
there must be a double apparatus of microscopes, &c. to use 
when the instrument is reversed. 

In conclusion, it may perhaps be proper to add, since some 
gentlemen may feel inclined to ask, How my instrument lias 
performed ? whether in actual observation it does what was 
expected from it ? To this, I think, I now may fairly answer 
in the affirmative ; that I do find it a very useful instrument, 
and the best adapted, of any that I know, to the perfecting of 
our catalogues. For some time, I will confess, I had my doubts, 
I received it in the beginning of the winter, when the cold 
and dark weather made all examination of it irksome. As a 
transit-instrument, I soon was satisfied with its performance, 
even in respect of the pole star itself. It is very steady ; and 
rarely wants any re-adjustment at all. As a circle, I was not. 
The deviation of the axis, though both ends, as far as I could 

mdccxciii. X 


150 Mr. Wollaston's Description 

judge, seemed always to deviate equally, perplexed me much ; 
and destroyed all confidence. The collimation in altitude 
(whose error when constant, is unimportant) appeared va- 
riable ; and seemed to give uncertain conclusions. Whether 
that took its rise from the object-glass, or the wires ; from the 
hanging of the plumb-line, or the microscopes ; was doubtful. 
All these things it took up much time to investigate. But I 
think I now may say, these difficulties are all surmounted. 
The error in the Y s, it has been said already, is cured. The 
object-glass I suspected might have some little shake, from its 
being attached to a false tube on the outside, and therefore 
liable to be touched, instead of being within the tube of the 
telescope itself. This was made more certainly steady. The 
wires I was sure did not move. Neither did the microscopes, 
after I had set them perfectly at ease ; for I found that in the 
first placing, I had a little cramped one of them. The dots 
came then to be examined, by which the plumb-line is ad- 
justed ; or rather, I should say, by which the circle is brought 
into a position for adjusting the microscopes. Here a small 
error was discovered, ft has been mentioned already, that 
there are four pair of dots for this purpose. Though laid off, 
I am satisfied, at first with the greatest care, and strictly true; 
the opening or enlarging of them afterwards, to make them 
just visible on each side of the plumb-line, had occasioned 
some very small differences in them, in respect of their ad- 
joining divisions or dots on the limb. The adjusting there- 
fore to a different pair of these dots, which I had done, would 
necessarily occasion a difference in the collimation. This be- 
ing avoided, by using always the same ; and other causes of 
error being removed ; the collimation for altitude seems now 


of a Transit Circle. 151 

to be as steady as can well be desired. I had more of these 
dots ; because, the instrument being new, I could not be cer- 
tain in what position it might be found most convenient to 
adjust. I now do it always with the telescope pointing to the 
zenith ; and in another instrument, I should recommend the 
having no more than two dots for that purpose. 

Some small errors I do perceive, which I believe are to be 
ascribed to the great power of my microscopes, which are too 
strong for works of art. It was against the judgment of Mr. 
Cary that they magnified so much ; and I believe he was in 
the right. Some errors are certainly to be laid to the charge 
of my own eyes, which do not define objects as they used to 
do. But in general, I may fairly say, my observations of the 
same star, seldom differ from each other above 5 seconds in 
altitude, and most commonly they are much within that 
limit. 

In observing, I always study to be as much at my ease as 
possible : and therefore I always sit, and use a prismatic eye- 
glass. To avoid touching the instrument itself, or even the 
stone on which it stands, I have four upright poles from the 
floor to the roof, with cross braces on a level with the bottom 
plate of the instrument ; against which I may lean, while I 
observe, or when I handle any part of the instrument. These 
I find to be of great comfort and use. Against two of the 
poles I hang a curtain occasionally, to keep off the sun, or to 
lessen the false light when I observe a star in the day. 

The two exterior horizontal wires, mentioned above, I find 
very convenient. They are really if 43", 5 of a great circle 
distant from the centre. By means of them, I can, without 
any hurry, observe the preceding limb of the sun at 3 wires ; 

X 2 


152 Mr. Wollaston's Description 

then set the lower limb to the upper wire, and read that off ; 
set the upper limb to the lower wire ; am ready to observe 
the second limb of the sun at the 3d, 4th, and 5th wires ; 
and lastly, read off the upper limb after the observation is 
ended. In this way, one has the meridian passage through 
the middle of the field, or within 2' of it : and the meridian 
altitude of both the limbs, while the sun's centre is on the 
meridian ; for the little alteration in altitude is soon done, and 
can disturb nothing. 

Indeed, upon the whole, this instrument itself is capable of 
doing a great deal of good work ; and convinces me fully, that 
one between piers would be highly advantageous to astro- 
nomy. As a transit, mine is perfect, so far as that size per- 
mits : indeed it is in fact to all intents a transit-instrument. 
And for altitudes ; since the readings are totally independent 
of the circle, though you have it in your power to re-examine 
your microscopes by the plumb-line between each observa- 
tion, if you please ; you find there is no occasion for it. In that 
respect, it has the advantage over a quadrant. No force is 
used in setting this instrument : the whole, from its form, 
is counterpoised in itself : there is no more probability of de- 
ranging it in altitude, than in azimuth : and therefore, all 
you have to do in actual observation beyond a common 
transit-instrument, is, to bisect the star as it passes, or as 
soon as ever it has passed the meridian wire, and read off 
the microscopes afterwards. Thus every observation is com- 
plete; by ascertaining the right ascension and altitude of 
every object at once, and with very little trouble ; which 
must tend greatly to the improvement of our catalogues. 

There is one additional advantage in an instrument of 




1 


Philos, '/ra-ns-lsi DCCXC1TI. TaO. XV. 




■S 



« 






- V 




f 








\ 




153 


of a Transit Circle. 

this form ; that you have it in your power to reverse the 
whole in a few minutes without any hazard ; which I do re- 
gularly ; because thereby you discover, and destroy, any 
errors which there may be in the instrument itself, or which 
may at any time arise in observing. 


C 154 3 


XIII. Description of an extraordinary Production of Human 
Generation , with Observations. By John Clarke, M. D . 
Communicated by Sir Joseph Banks, Bart. P. R. S. 

Read May 1 6, 1793. 

In the course of the last year, a woman was admitted into 
the General Lying-in Hospital, in Store Street, Tottenham- 
court Road, who, after a natural labor, was delivered of a 
healthy child. 

The birth of this child was succeeded, however, by a repeti- 
tion of uterine contractions, by which another substance was 
expelled, which is the subject of this paper. 

It was inclosed in a distinct bag of membranes, composed 
of decidua, chorion, and amnios, and had a placenta belong- 
ing to it ; the side of which was attached to the placenta of 
the perfect child. The membranes had been opened before I 
saw it, and a small quantity of liquor amnii having been dis- 
charged, the contents of the cavity were exposed. 

The substance contained in the membranes was of an oval 
figure, rather flattened on the two sides. Its long diameter 
was about four inches ; and its short diameter, from edge to 
edge, three inches. One edge was rather more concave than 
the other, and near the centre of it there was a small and thin 
funis, in length about an inch and half, by means of which it 
was connected to the placenta. 


Dr. Clarke's Description, &c. 155 

The surface of this substance was covered with the com- 
mon integuments, and from it issued four projecting parts. 
Of these the upper is an imperfect resemblance of the foot of 
a child, having one large and three smaller toes upon it. The 
lower is a still more imperfect imitation of a foot, having 
one large and two smaller toes. 

Between the two feet is situated a small and rounded pro- 
jection ; into which a small passage led, capable of contain- 
ing a large bristle, but it soon terminated in a cnl de sac. Close 
to the funis there was another small and thin projection, about 
a third of an inch in length, which looks like a finger, and was 
found to contain bony matter, and joints. 

There was no appearance of head, or neck. No ribs could 
be felt, nor clavicle, nor scapula. There was no vestige of 
any thing like legs, or thighs, or upper extremities ; or of 
organs of generation. 

The only external similarity of this monster to a human 
foetus, consists of its covering, and the attempt at a formation 
of two feet, and a finger. 

Before the internal structure was examined, the navel- 
string of the perfect foetus was injected, from whence the in- 
jection very readily passed through both placentae, viz. that 
of itself, and that of the monster ; and then into the substance 
of the monster also, as appeared by the redness of the skin. 

When the injection had become cold, the skin was care- 
fully dissected off; in doing which it was found that the up- 
per foot had no bony connection, but grew loose, and only 
connected to the internal parts by cellular substance. The 
lower foot was articulated to the inferior part of the tibia and 
fibula. 


15b Dr. Clarke's Description of an extraordinary 

The internal structure of the monster was composed of soft 
and bony matter. Upon cutting into the former, it appeared 
of a homogeneous fleshy texture, but without any regular or 
distinct arrangement of muscular fibres ; and was very vascu- 
lar throughout. 

The bones which were surrounded by this fleshy substance 
were, the os innominatum, the os femoris, the tibia, and the 
fibula. The relative situation of these to each other de- 
scribed the attitude of kneeling. With regard to the bones 
themselves, the os innominatum, and the os femoris are both 
perfect, and of the size which we meet with in a foetus at the 
full period of utero-gestation ; but the tibia and fibula are 
much shorter than in their natural proportion to the thigh bone. 

At the upper part, and towards the inside of the os innomi- 
natum, was placed a little portion of small intestines, loosely 
connected, by their mesentery, to the posterior edge of that 
bone, where it is commonly united to the os sacrum. These 
intestines had a covering of peritonaeum, and were very mi- 
nutely injected. 

The next object was to trace the vessels of the funis, which 
was done with great care. There appeared to be only two, 
viz. an artery, and a vein ; and these passed on towards the 
inner surface of the os innominatum. As they approached 
this bone, they gave off some branches to the surrounding 
parts, which quickly became too small to be traced. The 
trunks then passed backward, towards that part where the 
articulation with the os sacrum is generally found ; at which 
place they went to the other side of the bone, where they 
distributed a great number of small branches, and were at 
length lost in the surrounding parts. 


Production of Human Generation, & c. 

This was the whole of the internal construction of this very 
extraordinary monster. There was not the smallest appear- 
ance of head, or vertebras, or ribs. There was neither brain, 
spinal marrow, nor nerves. It had no heart, nor lungs. It 
contained none of the viscera subservient to digestion, except- 
ing the intestines already mentioned ; nor any glandular sub- 
stance whatsoever. 

This being a monster of so singular a nature, I shall beg 
leave to add, to the foregoing description, a few observations, 
which the circumstances appear to me naturally to suggest. 

The mere description of any monster is of very small 
utility, unless it tends to explain some actions of the animal 
economy, before imperfectly, or not at all understood. It is 
on this account that very little addition has been made to the 
stock of our knowledge of natural history, from considering 
those monsters in which there are either supernumerary or 
confused parts ; because, if we cannot distinctly perceive the 
use, or necessity of parts, in their natural state, we are not 
likely to advance in information by the examination of those 
varieties of structure, where difficulties are only multiplied by 
the greater complication, or aggravated by the confusion of 
p&rts. The only useful inference in natural history, which can 
be drawn from monsters of the last kind is, that nature can 
deviate from the usual arrangement of parts, without any 
material inconvenience ; and therefore, that the existence of 
parts so as to be capable of being applied to the purpose for 
which they are intended, in the perfect state of the system, 
rather than any precise order of them, is required for carry- 
ing on the functions of an animal body. 

Monsters, however, where considerable parts are wanting, 

Y 


JMDCCXCIXI. 


1,58 Dr. Clarke's Description of an extraordinary 

seem peculiarly likely to assist in the prosecution of physiolo- 
gical researches. 

If we were never to see an animal except in its perfect 
state, we could form no just idea of the comparative necessity 
of the different parts. So also, if we were to attend alone to 
the complete structure which obtains in the more perfeckani- 
mals, we might be led falsely to conclude, that the usual 
connexion of parts, which we find in them, was essential to 
the structure and composition of animal matter. Of these 
parts, the brain and nerves, the stomach and digestive organs 
generally, the heart, and the lungs, would appear to be of 
such importance in the machine, that one would be induced 
to imagine that the functions of life could not be carried on 
without them : but in tracing the works of nature down- 
wards, we shall at length find animals gradually becoming 
more and more simple in their construction. The brain and 
nervous system are altogether wanting in some, and there 
are others which have neither heart nor lungs ; yet they 
continue to exist, and are capable of performing the most im- 
portant functions of animals. Thus the formation of one 
animal serves to throw light upon the economy of others. 

This great simplicity of structure is found, however, 
chiefly in animals the texture of whose bodies is nearly ho- 
mogeneous ; not consisting, as in more perfect animals, of 
parts so different from each other, as skin, intestines, &c. are 
from bone. 

It might therefore still be supposed, that all the compli- 
cated mechanism, found in the more perfect animals, is 
essential to the construction of such heterogeneous sub- 
stances, as those of which they consist. 


Production of Human Generation, &c. 159 

To investigate this matter, we must have recourse to those 
monsters in which there is a deficiency of parts. 

There is a very material difference between the nature of 
the life of the more perfect animals, during their time of 
foetal existence, and after that they are born. In the latter 
state, the brain and nerves appear to be so essential, that any 
very considerable defect in them is incompatible with the 
well-being of the animal ; but in the uterine state, consi- 
derable deviations from the ordinary arrangement of parts, 
and such as cannot be endured after birth, are supported, 
without any inconvenience. 

The brain has been frequently found very incompletely 
formed, and sometimes not at all, yet still there have been 
nerves. In other cases, where the brain has been perfect, the 
spinal marrow has been deficient in a great part of its extent, 
and sometimes throughout. 

Both these occurrences are sufficient to prove, that, at any 
rate, that intimate connexion of the brain and nervous sys- 
tem, which takes place after birth, is not necessary for the 
formation of a body in other respects perfect. But still it 
would remain doubtful, whether any regular structure could 
be formed, without any vestige of either brain, or nerves ; 
and therefore without a possibility of their influence, in any 
manner, toward such structure. 

The monster now under consideration is so extremely 
simple, in this respect, that it cannot be exceeded by the most 
simple animal known. 

It may be objected, however, that there might be brain, or 
nervous fibres, in this monster, but that they might, in the 
dissection, be destroyed. But, in the first place, I beg leave 

Ye 


160 Dr. Clarke's Description of an extraordinary 

to observe, that the parts were examined too carefully for 
such a suspicion ; and, in the next, as there were no bones 
representing either the cranium, or spine, or os sacrum, it is 
not probable that their contents should exist in any other 
situation. 

Another objection may perhaps be taken from the anasto- 
mosis of the vessels of the monster, with those of the perfect 
foetus, and it may be assumed, that the nervous influence 
might be transmitted, in this way, along the vessels ; but 
there is very good reason for believing that the vessels of the 
placenta have no nerves, since, when we cut the navel-string, 
neither the mother, nor the child, expresses the smallest sign 
of sensation : and indeed', even if they had nerves, it is still 
very unlikely that, merely by such anastomosis, any nervous 
influence could be conveyed. 

I think it right to answer another possible objection which 
may be made, viz. that nervous matter may be co-extended, 
or co-existent with all other animal matter, and that, of 
course, it is of no consequence whether there be any sen- 
sorium, or reservoir of impressions, &c. or not ; because the 
stimulus, which produces action, must reside in parts, as well 
as the other substance of which they are composed. 

Now, although this may possibly be true, we have no evi- 
dence of the fact sufficiently satisfactory to carry conviction 
along with it. On the contrary, there seems to be good 
reason for entertaining an opinion, that nervous influence is 
conveyed from the brain downwards. If we are right in this 
conjecture, which is warranted by the experiment of tying, 
or cutting nerves, then the existence of the nervous fibre, 
like that of a string of a musical instrument, would be inactive. 


Production of Human Generation, &c. 161 

unless it received an impression, which, with regard to the 
nerves, should come from the brain. 

The whole of the actions of this monster, then, must have 
been those of the vascular system entirely ; and these seem 
to have been capable of forming bone, skin, cellular substance, 
ligament, cartilage, intestines, &c. 

The defect of heart (not an uncommon kind of mon- 
strosity) proves, that the energy of the arteries was equal to 
carrying on the circulation, not only in its own body, but 
also through its own placenta. 

The deficiency of nerves renders it extremely probable that 
their use is very small, if any, to the embryo. 

It has been an opinion, entertained by a very acute physio- 
logist, Mr. John Hunter, that, in all cases, a foetus is a 
very simple animal, as to its internal actions, and the circum- 
stances attending this monster fully confirm his idea. 

The usual objects of nature in the formation of a foetus 
are, that it should grow, and that it should be fitted with 
parts which, though of no use to it then, are essential after- 
wards. We know that the lungs are of this kind, and it is 
very likely that the brain and nerves are so too.* 

The common uses of the nervous powers are, to convey im- 
pressions from without, and volition from within. Now a 
foetus in the uterus is exposed to no external impressions, and 
is most probably incapable of volition, since it is not con- 

* That there is a very material difference between the internal functions of a foetus 
in the womb, and those of an infant after birth, seems very presumable ; not only 
from finding that it can carry on life without parts which are of the greatest moment 
afterwards ; but also from its possessing parts which after birth go into decay, or dis- 
appear, as the thymus gland, &c. 


i 6q Dr, Clarke’s Description of an extraordinary 

form able to the general wisdom of nature to give that which, 
in such a situation, must be useless. 

The whole growth then, and formation of a foetal body, 
would seem to depend upon the actions of the vascular ap- 
paratus, which, if we may be permitted to judge from this 
instance, is fully equal to the task. 

With regard to the manner in which this monster was 
supplied with nourishment, and with the benefit of air, there 
is nothing remarkable ; because it had a placenta, and the 
circulation between it and the mother was the same as in 
the most perfect foetus. 

Tab. XVII. and XVIII, 

Exhibit the appearances described in the foregoing paper. 

Tab. XVII. A view of the external appearances. 

A. An imperfect formation of a foot, with four toes upon it. 

B. An imperfect formation of another foot, having three 
toes upon it. This foot was connected to the tibia and 
fibula. 

C. The projection into which a duct led, terminating in a 
blind pouch. 

D. The funis umbilicalis. 

E. An imperfect formation of a finger. 


Tab. XVIII. An internal view of the parts, as they appeared 
after clearing away the fleshy matter from the bones. 

A. The os innominatum. 

B. The os femoris. 



<fcs. 










25 u.g U/u rfjb 


I 


. 

\ 


X 




c 










- Production of Human Generation, &c. 163 

C. The tibia and fibula, to which the lower foot was con- 
nected. 

D. The funis umbilicalis, with two bristles in the vessels. 

E. The bristles passing, in the vessels, to the outside of the 
os innominatum. 

F. A portion of small intestines, terminating in a cut de sac 
at each extremity. 


XIV. Description of an Instrument for ascertaining the specific 
Gravities of Fluids. By John Godfrey Schmeisser. Commu- 
nicated by Sir Joseph Banks, Bart . P. R. S. 


Read May ib, 1793. 


Although it be well known to chemists, as well as to ex- 
perimental philosophers in general, that the ascertaining the 
specific gravities of bodies is a matter of great importance in 
various chemical experiments, as well as in the analysis and 
chemical investigation of different substances ; yet we find 
that this precaution is too frequently neglected in the ac- 
counts given of the experiments by the authors themselves, 
and that the neglect of it has sometimes occasioned the failure 
of these very experiments, when repeated by others. 

As this defect has, in a great measure, arisen from the want 
of an accurate and convenient apparatus, a defect which I 
have formerly experienced myself, I have for some time past 
employed my thoughts in inventing a contrivance by which 
this difficulty might be removed. I flatter myself that I 
have now succeeded ; having contrived an instrument, which 
I have found to answer every purpose for which it was in- 
tended, to my great satisfaction ; so that the specific gravities 
of fluids may be determined in an easy and accurate manner. 

Every ingenious man will easily convince himself in what 
respect this instrument may differ from, or how far it may be 


Mr. Schmeisser's Description of an Instrument, &c. 165 

preferable to, those which have been hitherto made public ; 
and even to that lately invented and recommended by Mr. 
Rams den. 

The whole apparatus is represented in Tab. XIX. fig. 1 ; it 
consists of a flat-bottomed glass bottle (fig. 2) in which is 
fitted, by grinding, a glass stopper having a thermometer 
passing through it, (fig. 3.) The bore of this stopper is coni- 
cal, (fig. 4) and the thermometer has a glass collar, (fig. 5) 
which is ground into the bore of the stopper, so as to be per- 
fectly tight. There is some difficulty both in making the glass 
collar, and in fitting it into the stopper. If the thermometer 
tube and the collar be not made of the same metal, the collar 
is very apt to fly off in grinding ; for this reason I have some- 
times fixed the tube into the stopper by means of a thin piece 
of elastic gum, wound very tight round the tube. This gum, 
by its elasticity, effectually excludes air and liquids, and is, in 
the usual temperature of the atmosphere, not dissolved by 
any liquor, except vitriolic aether, and not even by that, un- 
less it is particularly prepared for the purpose. 

The cavity left at the upper part of the stopper may be 
filled up with sealing w r ax, or any other kind of cement ; this 
will assist in fixing the tube, and as the liquors to be weighed 
do not come in contact with this part, if the bottle be care- 
fully filled, there is no danger that the wax, or cement made 
use of, should in any degree affect the accuracy of the ex- 
periments. 

I have made, at different times, comparative experiments 
with this instrument, with a view to the further ascertaining 
its accuracy, and the different improvements made in it ; 
and I can with much confidence assert, that I have never 

MDCCXCII I. Z 


1 66 Mr. Schmeisser's Description of an Instrument 

found either the least difference in the results, or any thing 
else contrary to my expectations. 

The manner of using this instrument, and preparing it for 
experiments, is as follows. 

(1.) A. An accurate cubic inch, which is fastened, by 
means of a horse-hair, to a hydrostatic balance, is to be sus- 
pended in a vessel with distilled water, of the temperature of 
6 o degrees, according to Fahrenheit ; when the sum of the 
weight which the cubic inch thus loses, in the water, will be 
equal to the weight of an equal quantity of water displaced 
by it. 

(2.) B. The instrument, free from moisture, is then to 
be put into the scale of an accurate balance, and its weight 
ascertained, from which the weight of the common air con- 
tained in the bottle must be deducted ; when the remainder 
will indicate the absolute weight of the instrument. 

(3.) C. The bottle of the apparatus is then to be filled 
with distilled water, of the temperature of 60 degrees, and 
the stopper, with the thermometer, fitted to the bottle, so that 
neither the smallest bubble of air may remain in it, nor any 
of the fluid adhere to the outside of the stopper or bottle ; 
after which the weight of the water is to be ascertained, and 
marked upon the bottle, from which, by calculation accord- 
ing to experiment A, the quantity of water, contained in the 
bottle in cubic inches measure, may be found. Having thus as- 
certained the quantity of water of bo degrees of temperature 
which the bottle contains, the bottle may then be filled with 
any other fluid of the same temperature, and its weight as- 
certained, according to experiment C, and compared with 
that of distilled water. If, for example, the bottle be found 


Philos. Frans. MDCCXCDI. Tab. XIX. p. ,66. 





for ascertaining the specific Gravities of Fluids. 167 

to contain 327 grains of distilled water, and 654 of another 
fluid, the difference will be as 1 to 2 ; or 654 divided by 
327, will give 2 for the quotient. The specific gravity then, 
of the fluid thus found, compared with that of distilled water, 
is properly expressed by the ratio 2,000 : 1,000 ; which latter 
expression is taken for the standard. 

As ft is a known fact that fluids exhibit different specific 
gravities at different temperatures, it would have been ne- 
cessary for me to form a table, exhibiting the specific gra- 
vities of fluids at different temperatures, had I not, in order 
to avoid this inconvenience, hit upon a method of bringing the 
fluids, whose specific gravities are to be investigated, to a cer- 
tain standard, viz. to 60 degrees, by setting the bottle with 
the fluid in a glass vessel with cold water, and adding as 
much warm water as may be necessary to bring that fluid to 
this standard of 60 degrees. 

As the fluor acid will in some measure dissolve the glass, 
it becomes necessary, when that acid is to be weighed, to coat 
the inside of the bottle, by melting a little bees-wax in the 
bottle, and turning it, with the thermometer, in such a man- 
ner that the inside, together with the lower part of the ther- 
mometer, may become totally covered when cooled ; which 
coating may easily be removed by means of a little oil of 
turpentine, or any other essential oil, all of which dissolve 
wax very readily. 


C 168 3 


XV. Extract of a Letter from Sir Charles Blagden, Knt . 
Sec. R. S. to Sir Joseph Banks, Bart. P. R. S. giving some 
Account of the Tides at Naples. 

Read May 2, 1793. 

Rome, March 30, 1793. 

I took some pains at Naples to get information about 
the state of the tides, but could learn nothing satisfactory. 
The quantity of rise and fall is so little, that unless the sea 
be very calm, it is impossible to make a good observation. 
One of the best places for ascertaining the phenomena would 
be at what they call the river Styx, which is a narrow com- 
munication between the Porto di Miseno and the Mare Morto. 
Here I learned very distinctly that the water sometimes ran 
in, and sometimes out, but could not get the times ; when I 
was there it was running out. The best observation I had 
was on the 2d of March, when it appeared to be high water 
at Naples about eleven in the forenoon, and low water be- 
tween five and six in the afternoon ; with a difference of 
pretty exactly one foot in the height. The wind blew the 
same way ail the time, and the sea was very little agitated. 
On the preceding day the water had sunk an inch or two 
lower. From this observation, as well as some others less ac- 
curate, I concluded the time of high water at full and change 
to be between nine and ten o'clock, in the Bay of Naples. 

I am, &c. 


C. BLAGDEN. 


XVI. Observations on Vision. By Thomas Young. Communi- 
cated by Richard Brocklesby, M.D. F. R. S. 


Read May 30, 1793. 

It is well known that the eye, when not acted upon by any 
exertion of the mind, conveys a distinct impression of those 
objects only which are situated at a certain distance from it- 
self ; that this distance is different in different persons, and 
that the eye can, by the volition of the mind, be accommo- 
date’! to view other objects at a much less distance : but how 
this accommodation is effected, has long been a matter of 
dispute, and has not yet been satisfactorily explained. It is 
equally true, though not commonly observed, that no exer- 
tion of the mind can accommodate the eye to view objects at 
a distance greater than that of indolent vision, as may easily 
be experienced by any person to whom this distance of indo- 
lent vision is less than infinite. 

The principal parts of the eye, and of its appertenances, 
have been described by various authors. Winslow is ge- 
nerally very accurate ; but Albinus, in Musschenbroek j s 
In ro-‘u tii, has represented several particulars more correctly. 
I shall suppose their account complete, except where I men- 
tion or delineate the contrary. 

The first theory that I find of the accommodation of the 


170 Mr. Young's Observations on Vision . 

eye is Kepler's. He supposes the ciliary processes to contract 
the diameter of the eye, and lengthen its axis, by a muscular 
power. But the ciliary processes neither appear to contain 
any muscular fibres, nor have they any attachment by which 
they can be capable of performing this action. 

Descartes imagined the same contraction and elongation 
to be effected by a muscularity of the crystalline, of which he 
supposed the ciliary processes to be the tendons. He did not 
attempt to demonstrate this muscularity, nor did he enough 
consider the connection with the ciliary processes. He says, 
that the lens in the mean time becomes more convex, but at- 
tributes very little to this circumstance. 

De la Hire maintains that the eye undergoes no change, 
except the contraction and dilatation of the pupil. He does 
not attempt to confirm this opinion by mathematical demon- 
stration ; he solely rests it on an experiment which has been 
shewn by Dr. Smith to be fallacious. Haller too has 
adopted this opinion, however inconsistent it seems with the 
known principles of optics, and with the slightest regard to 
hourly experience. 

Dr. Pemberton supposes the crystalline to contain muscu- 
lar fibres, by which one of its surfaces is flattened while the 
other is made more convex. But, besides that he has demon- 
strated no such fibres. Dr. Jurin has proved that a change 
like this is inadequate to the effect. 

Dr. Porterfield conceives that the ciliary processes draw 
forward the crystalline, and make the cornea more convex. 
The ciliary processes are, from their structure, attachment, 
and direction, utterly incapable of this action ; and, by Dr, 


Mr. Young's Observations on Vision. 171 

Jurin’s calculations, there is not room for a sufficient motion 
of this kind, without a very visible increase in the length of 
the eye’s axis : such an increase we cannot observe. 

Dr. Jurin’s hypothesis is, that the uvea, at its attachment 
to the cornea, is muscular, and that the contraction of this 
ring makes the cornea more convex. He says, that the fibres 
of this muscle may as well escape our observation, as those of 
the muscle of the interior ring. But if such a muscle existed, 
it must, to overcome the resistance of the coats, be far stronger 
than that which is only destined to the uvea itself ; and the 
uvea, at this part, exhibits nothing but radiated fibres, losing 
themselves, before the circle of adherence to the sclerotica, in 
a brownish granulated substance, not unlike in appearance to 
capsular ligament, common to the uvea and ciliary processes, 
but which may be traced separately from them both. Now at 
the inferior ring of the uvea, the appearance is not absolutely 
inconsistent with an annular muscle. His theory of accommo- 
dation to distant objects is ingenious, but no such accommo- 
dation takes place. 

Musschenbroek conjectures that the relaxation of his ci- 
liary zone, which appears to be nothing but the capsule of the 
vitreous humour where it receives the impression of the ciliary 
processes, permits the coats of the eye to push forwards the 
crystalline and cornea. Such a voluntary relaxation is wholly 
without example in the animal economy, and were it to take 
place, the coats of the eye would not act as he imagines, nor 
could they so act unobserved. The contraction of the ciliary 
zone is equally inadequate and unnecessary. 

Some have supposed the pressure of the external muscles, 
especially the two oblique muscles, to elongate the axis of the 


17* Mr. Young's Observations on Vision. 

eye. But their action would not be sufficiently regular, nor 
sufficiently strong ; for a much greater pressure being made 
on the eye, than they can be supposed capable of effecting, 
no sensible difference is produced in the distinctness of vision. 

Others say that the muscles shorten the axis : these have 

still less reason on their side. 

<& 

Those who maintain that the ciliary processes flatten the 
crystalline, are ignorant of their structure, and of the effect 
required : these processes are yet more incapable of drawing 
back the crystalline, and such an action is equally inconsis- 
tent with observation. 

Probably other suppositions may have been formed, liable 
to as strong objections as those opinions which I have enu- 
merated. 

From these considerations, and from the observation of 
Dr. Porterfield, that those who have been couched have no 
longer the power of accommodating the eye to different dis- 
tances, I had concluded that the rays of light, emitted by ob- 
jects at a small distance, could only be brought to foci on the 
retina by a nearer approach of the crystalline to a spherical 
form ; and I could imagine no other power capable of pro- 
ducing this change than a muscularity of a part, or the whole, 
of its capsule. 

But in closely examining, with, the naked eye in a strong 
light, the crystalline from an ox, turned out of its capsule, I 
discovered a structure which appears to remove all the diffi- 
culties with which this branch of optics has long been ob- 
scured. On viewing it with a magnifier, this structure be- 
came more evident. 

The crystalline lens of the ox is an orbicular, convex. 


Mr. Young's Observations on Vision. 173 

transparent body, composed of a considerable number of si- 
milar coats, of which the exterior closely adhere to the inte- 
rior. Each of these coats consists of six muscles, intermixed 
with a gelatinous substance, and attached to six membranous 
tendons. Three of the tendons are anterior, three posterior ; 
their length is about two thirds of the semi-diameter of the 
coat ; their arrangement is that of three equal and equi- 
distant rays, meeting in the axis of the crystalline ; one of 
the anterior is directed towards the outer angle of the eye, 
and one of the posterior towards the inner angle, so that the 
posterior are placed opposite to the middle of the interstices 
of the anterior ; and planes passing through each of the six, 
and through the axis, would mark on either surface six regular 
equidistant rays. The muscular fibres arise from both sides of 
each tendon ; they diverge till they reach the greatest circum- 
ference of the coat, and, having passed it, they again con- 
verge, till they are attached respectively to the sides of the 
nearest tendons of the opposite surface. The anterior or pos- 
terior portion of the six viewed together, exhibits the ap- 
pearance of three penniformi-radiated muscles. The anterior 
tendons of all the coats are situated in the same planes, and 
the posterior ones in the continuations of these planes be- 
yond the axis. Such an arrangement of fibres can be ac- 
counted for on no other supposition than that of muscularity. 
This mass is inclosed in a strong membranous capsule, to 
which it is loosely connected by minute vessels and nerves ; 
and the connection is more observable near its greatest cir- 
cumference. Between the mass and its capsule is found a 
considerable quantity of an aqueous fluid, the liquid of the 
crystalline. 

2 A 


MDCCXCIII. 


174 Mr. Young's Observations on Vision . 

I conceive, therefore, that when the will is exerted to view 
an object at a small distance, the influence of the mind is 
conveyed through the lenticular ganglion, formed from 
branches of the third and fifth pairs of nerves, by the fila- 
ments perforating the sclerotica, to the orbiculus ciliaris, 
which may be considered as an annular plexus of nerves and 
vessels ; and thence by the ciliary processes to the muscle of 
the crystalline, which, by the contraction of its fibres, becomes 
more convex, and collects the diverging rays to a focus on 
the retina. The disposition of fibres in each coat is ad- 
mirably adapted to produce this change ; for, since the least 
surface that can contain a given bulk is that of a sphere, 
(Simpson's Fluxions, p. 4,86) the contraction of any surface 
must bring its contents nearer to a spherical form. The 
liquid of the crystalline seems to serve as a synovia in faci- 
litating the motion, and to admit a sufficient change of the 
muscular part, with a smaller motion of the capsule. 

It remains to be inquired, whether these fibres can pro- 
duce an alteration in the form of the lens sufficiently great to 
account for the known effects. 

In the ox's eye, the diameter of the crystalline is 700 thou- 
sandths of an inch, the axis of its anterior segment 225, of 
its posterior 350. In the atmosphere it collects parallel rays 
at the distance of 235 thousandths. From these data we find, 
by means of Smith's Optics, Art. 366, and a quadratic, that 
its ratio of refraction is as 10000 to 6574. FIauksbee makes 
it only as 10000 to 6832,7, but we cannot depend on his ex- 
periment, since he says that the image of the candle which 
he viewed was enlarged and distorted; a circumstance that he 
does not explain, but which was evidently occasioned by the 


Mr. Young's Observations on Vision. 


175 


greater density of the central parts. Supposing, with Hauks- 
bee and others, the refraction of the aqueous and vitreous hu- 
mours equal to that of water, viz. as 10000 to 74 65, the ratio 
of refraction of the crystalline in the eye will be as 10000 to 
8806, and it would collect parallel rays at the distance of 
1226 thousandths of an inch : but the distance of the retina 
from the crystalline is 550 thousandths, and that of the an- 
terior surface of the cornea 250 ; hence (by Smith, Art. 367,) 
the focal distance of the cornea and aqueous humour alone 
must be 2329. Now, supposing the crystalline to assume a 
spherical form, its diameter will be 642 thousandths, and its 
focal distance in the eye 926. Then, disregarding the thick- 
ness of the cornea, we find (by Smith, Art. 370,) that such 
an eye will collect those rays on the retina, which diverge 
from a point at the distance of 12 inches and 8 tenths. This 
is a greater change than is necessary for an ox's eye, for if it 
be supposed capable of distinct vision at a distance somewhat 
less than 12 inches, yet it probably is far short of being able 
to collect parallel rays. The human crystalline is susceptible 
of a much greater change of form. 

The ciliary zone may admit of as much extension as this 
diminution of the diameter of the crystalline will require; and 
its elasticity will assist the cellular texture of the vitreous hu- 
mour, and perhaps the gelatinous part of the crystalline, in re- 
storing the indolent form. 

It may be questioned whether the retina takes any part in 
supplying the lens with nerves ; but, from the analogy of the 
olfactory and auditory nerves, it seems more reasonable to sup- 
pose that the optic nerve serves no other purpose than that of 
conveying sensation to the brain. 

2 A 2 


i Mr. Young's Observations on Vision. 

Although a strong light and close examination are re- 
quired, in order to see the fibres of the crystalline in its intire 
state, yet their direction may be demonstrated, and their at- 
tachment shewn, without much difficulty. In a dead eye the 
tendons are discernible through the capsule, and sometimes 
the anterior ones even through the cornea and aqueous hu- 
mour. When the crystalline falls, it very frequently sepa- 
rates as far as the centre into three portions, each having a 
tendon in its middle. If it be carefully stripped of its cap- 
sule, and the smart blast of a fine blow-pipe be applied close 
to its surface in different parts, it will be found to crack ex- 
actly in the direction of the fibres above described, and all 
these cracks will be stopped as soon as they reach either of 
the tendons. The application of a little ink to the crystalline 
is of great use in shewing the course of the fibres. 

When first I observed the structure of the crystalline, I 
was not aware that its muscularity had ever been suspected. 
We have, however, seen that Descartes supposed it to be of 
this nature ; but he seems to think that the accommodation of 
the eye to a small distance is principally performed by the 
elongation of the eye's axis. Indeed as a bell shakes a 
steeple, so must the coats of the eye be affected by any change 
in the crystalline ; but the effect of this will be very incon- 
siderable ; yet, as far as it does take place, it will co-operate 
with the other change. 

But the laborious and accurate Leeuwenhoek, by the help 
of his powerful microscopes, has described the course of the 
fibres of the crystalline, in a variety of animals ; and he has 
even gone so far as to call it a muscle * ; but no one has pur- 

* Now if the cristaline humour (which I have sometimes called the crist. muscle) 


Mr. Young's Observations on Vision. 177 

sued the hint, and probably for this reason, that from examin- 
ing only dried preparations, he has imagined that each coat 
consists of circumvolutions of a single fibre, and has intirely 
overlooked the attachment of the fibres to tendons ; and if 
the fibres were continued into each other in the manner that 
he describes, the strict analogy to muscle would be lost, and 
their contraction could not have that effect on the figure of 
the lens, which is produced by help of the tendons. Yet not- 
withstanding neither he, nor any other physiologist, has at- 
tempted to explain the accommodation of the eye to different 
distances by means of these fibres, still much anatomical 
merit must be allowed to the faithful description, and ele- 
gant delineation, of the crystallines of various animals, which 
he has given in the Philosophical Transactions, Vol. XIV. p. 
780, and Vol. XXIV. p. 1723. It appears, from his descriptions 
and figures, that the crystalline of hogs, dogs, and cats, re- 
sembles what I have observed in oxen, sheep, and horses ; 
that in hares and rabbits, the tendons on each side are only 
two, meeting in a straight line in the axis ; and that in 
whales they are five, radiated in the same manner as where 
there are three. It is evident that this variety will make no 
material difference in the action of the muscle. 1 have not 
yet had an opportunity of examining the human crystalline, 
but from its readily dividing into three parts, we may infer 
that it is similar to that of the ox. The crystalline in fishes 
being spherical, such a change as I attribute to the lens in 
quadrupeds cannot take place in that class of animals. 

It has been observed that the central part of the crystalline 

in our eyes, &c. Phil. Trans. Vol. XXIV. p. 1729. — CrystaUimun mmculum, 
alias humcrem crystallinum dictum, &c. Leeuwenh. op. omn. I. p. 102. 


178 Mr. Young's Observations on Vision . 

becomes rigid by age, and this is sufficient to account for 
presbyopia, without any diminution of the humours ; although 
I do not deny the existence of this diminution, as a concomi- 
tant circumstance. 

I shall here beg leave to attempt the solution of some 
optical queries, which have not been much considered by 
authors. 

1. Musschenbroek asks. What is the cause of the lateral 
radiations which seem to adhere to a candle viewed with 
winking eyes ? I answer, the most conspicuous radiations are 
those which, diverging from below, form, each with a vertical 
line, an angle of about seven degrees ; this angle is equal to 
that which the edges of the eyelids when closed make with a 
horizontal line ; and the radiations are evidently caused by the 
reflection of light from those flattened edges. The lateral ra- 
diations are produced by the light reflected from the edges of 
the lateral parts of the pupillary margin of the uvea, while its 
superior and inferior portions are covered by the eyelids. 
The whole uvea being hidden before the total close of the 
eyelids, these horizontal radiations vanish before the perpen- 
dicular ones. 

2. Some have inquired, Whence arises that luminous 
cross, which seems to proceed from the image of a candle in 
a looking-glass ? This is produced by the direction of the 
friction by which the glass is polished : the scratches placed 
in a horizontal direction, exhibiting the perpendicular part of 
the cross, and the vertical scratches the horizontal part, in a 
manner that may easily be conceived. 

3. Why do sparks appear to be emitted when the eye is 
rubbed or compressed in the dark ? This is Musschenbroek's 


Mr. Young's Observations on Vision. 179 

fourth query. When a broadish pressure, as that of the 
finger, is made on the opaque part of the eye in the dark, an 
orbicular spectrum appears on the part opposite to that which 
is pressed : the light of the disc is faint, that of the circum- 
ference much stronger ; but when a narrow surface is ap- 
plied, as that of a pin's head, or of the nail, the image is nar- 
row and bright. This is evidently occasioned by the irritation 
of the retina at the part touched, referred by the mind to the 
place from whence light coming through the pupil would fall 
on this spot ; the irritation is greatest where the flexure is 
greatest, viz. at the circumference, and sometimes at the centre, 
of the depressed part. But in the presence of light, whether 
the eye be open or closed, the circumference only will be lu- 
minous, and the disc dark ; and if the eye be viewing any 
object at the part where the image appears, that object will be 
totally invisible. Hence it follows, that the tension and com- 
pression of the retina destroys all the irritation, except that 
which is produced by its flexure ; and this is so slight on the 
disc, that the apparent light there is fainter than that of the 
rays arriving at all other parts through the eyelids. This ex- 
periment demonstrates a truth, which may be inferred from 
many other arguments, and is indeed almost an axiom, viz. that 
the supposed rectification of the inverted image on the retina 
does not depend on the direction of the incident rays. Newton, 
in his sixteenth query, has described this phantom as of pavo- 
nian colours, but I can distinguish no other than white ; and it 
seems most natural that this, being the compound or average 
of all existing sensations of light, should be produced when 
nothing determines to any particular colour. This average 
seems to resemble the middle form, which Sir Joshua Rey- 


iBo Mr. Young's Observations on Vision. 

nolds has elegantly insisted on in his discourses ; so that per- 
haps some principles of beautiful contrast of colours may be 
drawn from hence, it being probable that those colours which 
together approach near to white light will have the most 
pleasing effect in apposit on. It must be observed, that the 
sensation of light from pressure of the eye subsides almost in- 
stantly after the motion of pressure has ceased, so that the 
cause of the irritation of the retina is a change, and not a dif- 
ference, of form ; and therefore the sensation of light appears 
to depend immediately on a minute motion of some part of 
the optic nerve. 

If the anterior part of the eye be repeatedly pressed, so as 
to occasion some degree of pain, and a continued pressure be 
then made on the sclerotica, while an interrupted pressure is 
made on the cornea ; we shall frequently be able to observe 
an appearance of luminous lines, branched, and somewhat con- 
nected with each other, darting from every part of the field of 
view, towards a centre a little exterior and superior to the axis 
of the eye. This centre corresponds to the insertion of the 
optic nerve, and the appearance of lines is probably occasioned 
by that motion of the retina which is produced by the sudden 
return of the circulating fluid, into the veins accompanying 
the ramifications of the arteria centralis, after having been 
detained by the pressure which is now intermitted. As such 
an obstruction and such a re-admission must require particu- 
lar circumstances, in order to be effected in a sensible degree, 
it may naturally be supposed that this experiment will not 
always easily succeed. 


F7ii7os. rrcms. MDCCXCIH. TabJ&L.p. m„. 





Mr. Young's Observations on Vision . 


181 


Explanation of the Figures. 

Tab.XX. fig. 1. A vertical section of the ox's eye, of twice 
the natural size. 

A. The cornea, covered by the tunica conjunctiva. 

BCB. The sclerotica, covered at BB by the tunica albugi- 
nea, and tunica conjunctiva. 

DD. The choroid, consisting of two laminas. 

EE. The circle of adherence of the choroid and sclerotica. 

FG, FG. The orbiculus ciliaris. 

HI, HK. The uvea : its anterior surface the iris ; its pos- 
terior surface lined with pigmentum nigrum. 

IK. The pupil. 

HL, HL. The ciliary processes, covered with pigmentum 
nigrum. 

MM. The retina. 

N. The aqueous humour. 

O. The crystalline lens. 

P. The vitreous humour. 

QR, QR. The zona ciliaris. 

RS, RS. The annulus mucosus. 

Fig. 2. The structure of the crystalline lens, as viewed in 
front. 

Fig. 3. A side view of the crystalline. 


2 B 


MDCCXCIII. 


t 182 3 


XVI L Observations on a Current that often prevails to the 
Westward of Scilly ; endangering the Safety of Ships that 
approach the British Channel. By James Rennell, Esq. 
F. R. S. 

1 

Read June 6, 1793. 

It is a circumstance well known to seamen, that ships, in 
coming from the Atlantic, and steering a course for the Bri- 
tish channel, in a parallel somewhat to the south of the Scilly 
Islands ; do, notwithstanding, often find themselves to the 
north of those islands : or, in other words, in the mouth of 
the St. George's, or of the Bristol channel. This extraordi- 
nary error has passed for the effects, either of bad steerage, 
bad observations of latitude, or the indraught of the Bristol 
channel : but none of these account for it satisfactorily ; be- 
cause, admitting that at times there may be an indraught, it 
cannot be supposed to extend to Scilly ; and the case has 
happened in weather the most favourable for navigating, and 
for taking observations. The consequences of this deviation 
from the intended track, have very often been fatal : particu- 
larly in the loss of the Nancy packet, in our own times ; and 
that of Sir Cloudesley Shovel, and others of his fleet, at the 
beginning of the present century. Numbers of cases, equally 
melancholy, but of less celebrity, have occurred ; and many 
others, in which the danger has been imminent, but not fatal, 
have scarcely reached the public ear. All of these have been 


Mr. Renneli/s Observations on a Current , &c. 183 

referred to accident ; and therefore no attempt seems to have 
been made, to investigate the cause of them. 

I am however of opinion, that they may be imputed to a 
specific cause ; namely, a current : and I shall therefore en- 
deavour to investigate both that, and its effects ; that seamen 
may be apprized of the times, when they are particularly to 
expect it, in any considerable degree of strength ; for then 
only, it is likely to occasion mischief ; the current that pre- 
vails at ordinary times, being, probably, too weak to produce 
an error in the reckoning, equal to the difference of parallel, 
between the south part of Scilly, and the track that a com- 
mander, prudent in his measures, but unsuspicious of a cur- 
rent, would chuse to sail in.* 

It seems to be generally allowed, that there is always a 
current, setting round the Capes of Finisterre, and Ortegal, 
into the Bay of Biscay. This I have the authority of Captain 
Mendoza Rios, a Fellow of the Royal Society, and an officer 
in the royal navy of Spain, for asserting. Besides, such an inti- 
mation was amongst the earliest notices that I received, con- 
cerning matters of navigation, when on board of a ship that 
sailed close along the north coast of Spain, in 1757. The cur- 
rent then, is admitted to set to the eastward, along the coast 
of Spain ; and continues its course, as I am assured, along the 
coast of France, to the north, and north-west: and indeed, 
any body of water, once set in motion, along a coast, cannot 

suddenly stop ; nor does it, probably, lose that motion, until 

• 

* It may be remarked, by the way, that the true latitude of the present light- 
house on St. Agnes’s Island, is 49 0 , 54'; and that of the most southerly part of the 
whole group of islands and rocks, is 49 0 , 52'. This is according to an advertisement 
giyen out by the Trinity House, in 1792. 

2 B 2 


184 Mr. Renneli/s Observations on a Current 

by degrees it mixes with the ocean ; after being projected 
into it, either from the side of some promontory, that extends 
very far beyond the general direction of the coast ; or after 
being conducted into it, through a strait. 

The original cause of this current, I apprehend to be, the 
prevalence of westerly winds in the Atlantic ; which, impel- 
ling the waters along the north coast of Spain, occasions a 
current, in the first instance. The stronger the wind, the 
more water will be driven into the Bay of Biscay, in a given 
time ; and the longer the continuance of the wind, the far- 
ther will the vein of current extend. 

It seems to be clearly proved, that currents of water, after 
running along a coast that suddenly changes its direction, (as 
happens on the French coast, at the promontory south of 
Brest) do not change their course with that of the shore, but 
preserve, for a considerable time, the direction which they re- 
ceived from the coast they last ran by. In some instances, 
after being projected into the sea, they never again approach 
the shore ; but preserve, to a very great distance, nearly the 
direction in which they were projected ; as well as a consi- 
derable degree of their original velocity, and temperature. 
The gulf stream (of Florida) is a wonderful instance of this 
kind ; which, originating in a body of pent-up waters, in the 
Gulf of Mexico, is discharged with such velocity, through the 
Straits of Bahama, that its motion is traceable through the At- 
lantic, to the Bank of Newfoundland ; and may possibly ex- 
tend much farther. This being therefore the case, we can 
have no difficulty in conceiving, that the current of the Bay of 
Biscay continues its course, which may be about NW by W, 
from the coast of F ranee, to the westward of Scilly and Ireland. 


that often prevails to the Westward cf Scilly. 185 

At ordinary times, its strength may not be great enough 
to preserve its line of direction, across the mouth of the Bri- 
tish Channel ; or, if it does preserve its direction, it may not 
have velocity enough to throw a ship so far out of her course, 
as to put her in danger. But, that a current prevails generally , 
there can be little doubt ; and its degree of strength will be 
regulated by the state of the winds. After a long interval of 
moderate westerly gales, it may be hardly perceptible ; for a 
very few miles of northing, in the 24 hours, will be referred 
to bad steerage, or some other kind of error : but after hard 
and continued gales from the western quarter, the current 
will be felt in a considerable degree of strength ; and not only 
in the parallel of Scilly, but in that of the south-west coast of 
Ireland likewise. 

Our observation of what passes in the most common 
waters, is sufficient to shew how easily a current may be in- 
duced, by the action of the wind, on the water contiguous to 
a bank, when the wind blows along it. In a canal of about 
four miles in length, the water was kept up four inches higher 
at one end, than at the other, by the mere action of the 
wind, along the canal. This was an experiment made, and 
reported to me, by my much lamented acquaintance, the late 
Mr. Smeaton. We know also, the effects of a strong south- 
west, or north-west, wind, on our own coasts : namely, that 
of raising very high tides in the British Channel, or in the 
Thames, and on the eastern coasts ; as those winds respec- 
tively blow : because the water that is accumulated, cannot 
escape quick enough, by the Strait of Dover, to allow of the 
level being preserved. Also, that the Baltic is kept up two 
feet at least, by a strong NW wind of any continuance : and 


i8(5 Mr. Renn ell's Observations on a Current 

that the Caspian Sea is higher by several feet, at either end, 
as a strong northerly, or southerly, wind prevails. There- 
fore, as water pent up, in a situation from which it cannot 
escape, acquires a higher level, so, in a place where it can 
escape, the same operation produces a current : and this cur- 
rent will extend to a greater or less distance, according to the 
force with which it is set in motion ; or, in other words, ac- 
cording to the height at which it is kept up, by the wind. 

It may possibly be asked, why a similar current does not 
prevail in the British Channel, from the same westerly winds? 
To this I answer, that the increased height and velocity of 
the tides, during the prevalence of such winds, prove that a 
part, at least, of the same effect which happens in the Bay of 
Biscay, is produced in the Channel ; and I have little doubt, 
that there is, in fact, a current also ; but that, as it is blended 
with the common tide, the effect on the senses is lost : for it 
may appear only in the form of a stronger flood tide, or a 
weaker ebb, than at other times. Whereas the Bay, a wider 
space, and of a different form, allows a freer scope to the 
tides, than the British Channel does : it being high water 
nearly at the same time, all over the Bay ; but varying in 
the Channel, at least five hours. And it may be concluded, 
from analogy, that the form of the Channel does not allow of 
the same effect being produced by ‘the wind, on its included 
waters, as may be produced on those of the Bay : these meet- 
ing with an opposition, in the coast of France, the others 
having a partial exit, at the Btrait of Dover : we may also 
conclude, that if no such phenomenon as a tide existed, a 
current, though less strong than in the Bay, would be per- 
ceived in the British Channel. 


that often prevails to the Westward of Scilly. 187 

Of the Bay of Biscay it may be observed that, by reason of 
its form, and exposure to the reigning winds, which are often 
violent, and which pass over a vast expanse of water, there 
is no part of the ocean, familiarly known to us, whose circum- 
stances are, in any degree, similar to it. It ought not there- 
fore to surprize us, if we find that it differs, in any particu- 
lar, from other seas. Seamen have remarked its uncommon 
degree of agitation, in stormy weather ; but this has not, as 
far as I know, been properly accounted for. May it not be 
owing generally, to the same cause as that which produces 
the current? and at times, to the very current itself? With 
respect to the first — the waves of a deep bay or gulf, when 
the wind forces the water into it, will meet with a resistance 
in the land at the head of it, which must occasion a reverbe- 
ration, that will render the surface of a great part of the gulf 
more unquiet, than when there is an opening at the end, to 
allow' the undulatory motion a freer scope. What is said here, 
is exemplified on a small scale, by Mr. Smeaton's very inge- 
nious manner of quieting Ramsgate harbour. (See his Tract 
on that harbour, page 45.) And with respect to the second 
cause — the effect of a current running to windward, in pro- 
ducing a short, hollow, and therefore dangerous, wave, is 
pretty well known. Accordingly, at seasons when the current 
runs strong, and the wind blows fresh from the north-west 
quarter, this cause must also contribute to the agitation of the 
waters, in the north part of the bay.* 

* How far the reverberatory motion may extend, I know not : but it is certain that 
an undulatory motion impressed on the sea by the wind, will extend to a prodigious 
distance ; and even into a region where a different wind prevails : as for instance, a 
swell raised by a strong gale, at south, or south-west, in the tract of variable winds. 


i88 Mr. Rennell’s Observations on a Current 

It is quite uncertain at what interval of time, from the 
commencement of strong westerly gales, in the Atlantic and 
Bay of Biscay, the current may operate on the tracks of ships,, 
near Scilly ; for we are not possessed of the data, requisite for 
determining it. If we were to conceive a current, originating 
on the coast of Spain, and afterwards disturbing the courses 
of ships, on the west of Scilly and Ireland ; this would re- 
quire too much time, to agree with one of the instances 
which I mean to adduce : although it is probable, that this 
may be nearly the effect at ordinary times, and when the 
westerly winds blow moderately. But as, in one striking in- 
stance, it appears that the current operated in a very remark- 
able manner, on the ship's course, on the fourth day after the 
commencement of the gale, in the quarter where the ship 
was ; the cause should rather be looked for, in the sudden and 
great accumulation of water, in the Bay of Biscay : otherwise, 
there is no accounting for the sudden appearance of the cur- 
rent. And the very act of accumulation, causing an in- 
draught, there will consequently be a current round the Capes 
of Finisterre, and Ortegal, towards the Bay. Be the exact 
cause, however, what it may, it no doubt originates in the 
Bay, by the action of strong westerly winds : the prevalence 
of such winds, will therefore be the signal for the appearance 
of a current, between Ushant, and the south-west coast of 
Ireland : for though the cause can only be guessed at, the ef- 
fect is too well ascertained, to remain in doubt. 

I shall now adduce the facts, ^on which the idea of the 
existence of a current is founded. 

has been felt, very far within the limits of the south-east trade wind, in the Indian 
Ocean. 


that often prevails to the Westzvard of Scilly. 189 

In crossing the eastern part of the Atlantic, in the Hector 
East India ship, in, 1778, we encountered, between the pa- 
rallels of 42 and 49, very strong westerly gales ; but particu- 
larly between the 16th and 24th of January, when, at inter- 
vals, it blew with uncommon violence. It varied two, or 
more, points, both to the north and south of west, but blew 
longest from the northern points ; and it extended, as I after- 
wards learnt, from the coast of Nova Scotia, to that of Spain. 

We arrived within 60 or 70 leagues of the meridian of 
Scilly, on the 30th of January, keeping between the parallels 
of 49 and 50 ; and about this time we began to feel a current, 
which set the ship to the north of her intended parallel, by 
near half a degree, in the interval between two observations 
of latitude ; that is, in two days. And the wind, ever after- 
wards, inclining to the south, would not permit us to regain 
the parallel ; for, although the northern set was trifling, 
from the 31st until we arrived very near Scilly; yet the 
wind, being both scant and light, we could never overcome 
the tendency of the current. Add to this, that the direction 
of the current, being much more westerly than northerly, we 
crossed it on so very oblique a course, that we continued in it 
a long time ; and were driven, as it appears, near 30 leagues 
to the west, by it : for we had soundings in 73 fathoms, in 
the latitude of Scilly, and afterwards ran 150 miles, by the 
log, directly east, before we came the length of the islands. 
In effect, in running 120 miles, we shallowed the water, only 
nine fathoms. 

We not only were sensible of the current, by the observa- 
tions of latitude, but by riplings on the surface of the water* 
and by the direction of the lead line. The consequence of all 

MDCCXCIII, 2C 


icp Mr. Rennell's Observations on a Current 

this was, that we were driven to the north of Scilly ; and 
were barely able to lay a course through The passage between 
those islands and the Land's End. 

Having no time keeper on board, we were unable to ascer- 
tain the several points, in this part of our track, and there- 
fore can only approximate our longitude ; and that but very 
coarsely. But according to what we learnt from our sound- 
ings, and from a vessel which had only just entered the cur- 
rent, it may be concluded, that the current, at times, extends 
to 60 leagues, west of Scilly ; and also runs close on the west 
of those islands. However, the breadth of the stream, may 
probably be little more than 30 leagues ; for we crossed it, as 
has been said, very obliquely ; and perhaps, in the widest 
part. 

The journal of the Atlas East India ship, Captain Cooper, 
in 1787, furnishes much clearer proofs, both of the existence 
of the current, and of the rate of its motion : for having time 
keepers on board. Captain Cooper was frequently enabled to 
note the difference between the true, and the supposed, 
longitude; and it may be said, that this journal, by the means 
it affords of ascertaining the current, is highly valuable ; as 
containing some very important facts, and which might have 
been entirely lost to the public, had not Captain Cooper 
marked them, in the most pointed manner. 

I shall proceed to state, in abstract, the most important of 
the facts recorded in the journal. 

The Atlas sailed with a fair wind, and took her depar- 
ture from the Isle of Wight, on the 25th of January, 1787 ; 
and on the 27th had advanced 55 leagues to the westward of 
Ushant ; when a violent gale of wind began at south, and. 


that often prevails to the Westward of Sciliy. 191 

about 11 hours afterwards, changed suddenly to the west- 
ward. The gale continued through the four following days : 
on the 28th, it was generally W by S, and WSW ; on the 
29th, SW by W, or more southerly ; and on the 30th and 
31st, SSW, to SW by S.* 

During this long interval, the ship was generally lying to ; 
and with her head to the NW. On the 1st of February, the 
wind abated, but" still blew from the south-westward ; and the 
ship was kept to the north-west. The stormy weather re- 
turned again the following day, and continued, with little 
intermission, until the 11th; blowing from all the interme- 
diate points, between south and WNW; but chiefly, and most 
violently, from the WSW, and SW. At intervals, on the 8th 
and 9th in particular, the journal remarks, that “ it blew a 
mere hurricane On the 11th, the weather growing more 
moderate, and the wind favourable, the ship proceeded on 
her course, southward ; being then two degrees and a quarter 
of longitude, to the west of Cape Finisterre, by the reckon- 
ing ; but by the time keepers, more than four degrees and a 
half. 

After the above abstract of the proceedings of the ship, I 
shall subjoin the following particulars ; which are the most in 
point, to the purpose of the present discussion. 

On the 27th, at noon, soon after the gale commenced, the 
longitude, by reckoning, agreed within 14 minutes of that 
shewn by the time keepers ; the latter being the most 
westerly. This difference alone might well have arisen from 

* In this, as well as in the former statement of the winds, I have allowed for the 
variation of the compass; that the application of it, to the quarter of the heavens, 
and to the chart annexed, (see Tab. XXI.) may be more easy and clear. 

2 C 2 


192 Mr. Rennell's Observations on a Current 

an error in the log, or even in the position of the needle 
point on the Isle of Wight, from whence the departure was 
taken ; but it may also be owing to the westerly current, 
whilst the ship remained in it, on the 27th ; if we admit that 
such a current prevails at all times, though in different de- 
grees of strength. Here it is proper to remark, that in deli- 
neating Captain Cooper's track, on the chart, I have scrupu- 
lously adhered to the result of each day's work, of the reckon- 
ing, as I find it in his journal ; contenting myself with in- 
serting my own observations on the track, in this paper 
only ; where they cannot mislead. 

The longitudes pointed out by the time keepers on the 
28th, 29th, and 30th, shew, that the increasing, though 
trifling differences, between the true longitude, and that by 
the dead reckoning, had amounted to 24 minutes only, on the 
30th. At this time the ship was about 24 leagues to the 
WSW of Scilly ; and, at 5 or 6 leagues to the SSE of this 
position, (that is, at 25 leagues SW by W from Scilly) they 
had soundings at 70 fathoms. This last particular is men- 
tioned, to prove that the longitude shewn by the time 
keepers (8° 28' west from London) was nearly the longi- 
tude in which the ship really was, on the 30th of January. 
That of St. Agnes (Scilly) is taken at 6° 46'. 

The Atlas was now entered into the stream of the same 
current which occasioned so much delay to the Hector ; 
but the course of the Atlas, being opposite to that of the 
Hector, it facilitated her progress ; and also carried her clear 
of the south-west coast of Ireland. 

On the 31st, the time keepers shewed that the ship had been 
set very considerably to the westward of the reckoning ; and by 


that often prevails to the Westward of Scilly. 193 

the 2d of February, at 3 in the afternoon, it appeared that 
she had been set two whole degrees of longitude to the west 
of the reckoning, since the 30th at noon ; that is, in the 
course of 51 hours. (Here it may be proper to remark, that 
I have, throughout, reckoned according to sea time ; that is, 
the day commences at noon.) 

On the 3d of February, at noon, the time keepers shewed 
a further set, of 23 minutes of longitude, more than the 
reckoning gave, in the interval since the last observation, 
which was 45 hours ; so that, since the 30th of January, 4 days 
only, the ship had been carried by the current, no less than 
two degrees and twenty-three minutes ; and since the 27th, 
when the gale began, 2 0 32' of longitude ; amounting, in these 
parallels, to ninety-nine marine miles. But here, the current 
appears to have totally left them ; and it is very probable, 
that it even ceased before the time of observation, on the 3d : 
for the succeeding observations of the 5th, 6th, 7th, 9th, 10th, 
and 11th, although the strong westerly gales continued, come 
so near the longitude by the reckoning (deduced from the 
observation of the 3d) that the differences, which are some- 
times to the east, and at other times to the west, may be 
with more propriety ascribed to errors of the log, than to a 
current; as may be seen by the two tracks on the chart. 
We may therefore conclude, that the current did not cease at 
the very point of time, when the observation of the 3d was 
taken, but probably some time before. 

It appears then, that the Atlas experienced a westerly cur- 
rent, from a point about 24 leagues to the WSW of Scilly, (if 
not earlier) to four degrees of longitude west of the meridian 


Mr. Renneli/s Observations on a Current 

of Cape Clear,* in the parallel of 5 T; where its effects were 
no longer perceptible. And, as no current was felt in the track 
southward, on the 1 ith ; nor in any part of the track to the 
north-west, between tire 3d and 10th ; although it was felt' 
nearly in the same line of direction, between the 1st and 3d; 
it may be inferred that the stream goes off to the north- 
west, between the aforesaid track, and the south-west coast of 
Ireland. It is much to be regretted that no observations ap- 
pear on the 12th and 13th ; which would have been decisive 
of its course. 

I come now to two particulars of the case, which, I con- 
fess, perplex me exceedingly. The first is, that the current 
was felt, apparently in its full strength, on the fourth day af- 
ter the commencement of the gale ; which began at south, 
then changed suddenly to the west and WSW, and after- 
wards fixed in the SW quarter. This gale was felt between 
the 48th and 50th degrees of latitude, and, no doubt, ex- 
tended its effects very far to the south and west ; but what 
the state of the winds had been in those quarters, previous to 
the 27th of January, we are ignorant. The winds in the Bri- 
tish Channel had been easterly, for three days preceding the 
gale : the fourth day, preceding, there had been strong gales 
at SW ; and the five days preceding that , there had been 
chiefly light winds at west. According to this state of facts, 
we can only suppose that the current originated from a vast 
body of water, pent up in the Bay of Biscay, by violent gales 
of wind ; first from the southward, eleven hours ; then from 
a point or two to the south cf west ; and lastly, at south-west, 

* Cape Clear is reckoned to be in long. 9 0 25' from London. 


*95 


that often prevails to the Westward of Scilly. 

We are not to consider the water of this current, as having 
made the circuit of the Bay of Biscay ; but as the collective 
body of pent up waters, in the Bay, running off along the SW 
coast of Britanny, and thence to the north-westward ; pre- 
serving nearly the direction it had acquired, by running along 
that coast. And it may be conceived, that the frequent recur- 
rence of westerly winds, keeps up a constant current in the 
Bay, and to some distance beyond it ; although during the 
longest intermissions of these winds, the current may become 
so slow, as to be scarce perceptible. 

The second particular which perplexes me, is, that no 
northern set is indicated by Captain Cooper's journal : that 
is to say, by the mode in which each day's log is wrought ; 
and which, in the formation of the chart, as is said before, I 
have strictly adhered to. It indeed appears to me very won- 
derful, that no northing should appear, when it seems to be 
the very same kind of current which carried the Hector so 
far to the northward. It is certain, that the state of the 
weather was such, as to preclude those nice attentions to the 
reckoning, which might enable us to detect any small dif- 
ferences, between the latitude by account, and that by obser- 
vation ; although the western set was too considerable to es- 
cape notice, and may even have been more than the state- 
ment sets forth. I cannot therefore, by any means admit, 
that there was no northing in the current through which the 
Atlas passed ; first, because they had not observations of lati- 
tude, regularly; and lastly, because on the 31st of January, 
when lying to, 36 miles are allowed for 20 hours drift, to the 
north-west ; which appears to me excessive. On that day 
they had no observation of latitude, and on the following 


Mr. Renneli/s Observations on a Current 


day, the observation shewed two miles northing ; which 
however proves nothing. Again, on the succeeding day, (the 
sd) in a most important point of the track, there was no ob- 
servation of latitude. 

In the Hector, precisely in the same track, and at the same 
season of the year, the current had, as has been observed, 
a considerable degree of northing in its course. On two days 
it was about 12 miles, each ; on another day 13, and on two 
others, and 8 ; and this, in weather very favourable for 
keeping a reckoning, and with observations of latitude, on 
every day save one ; not to mention the strong circumstances 
of a visible set to the northward, indicated, as well by the 
lead line, as by the ripling on the surface of the water. It is 
in the nature of currents, to expand their streams or columns 
of water, after being projected into the ocean ; and therefore, 
according to this law, the middle part of the stream should 
preserve its original course, in a greater degree than the 
borders of it ; so that the middle part may run to the 
NW by W, whilst the eastern border may run more nor- 
tberly, and the western border more westerly. It is certain, 
that in the Hector, we felt the northerly current much 
stronger, close on the west of Scilly, than further out ; and 
it appeared by the distance we ran, after sounding in 73 fa- 
thoms, that the current must have set much more westerly , 
than northerly, the whole time. 

The following remarks obviously occur, on the effect of this 
current. 

1st. Whatever may be the breadth of the stream, (which 
is at present unknown) if a ship crosses it very obliquely , that 
is, in an E by S, or more southerly direction (as may easily 


that often prevails to the Westward of Scilly. 197 

happen, on finding herself too far to the northward, at the 
first place of observation, after she gets into the current), 
she will, of course, continue much longer in it, and will be 
more affected by it, than if she steered more directly across 
it. She will be in a similar situation, if she crosses it with 
light winds ; and both of these circumstances should be at- 
tended to. And if it be true, as I suspect it is, that the eastern 
border of the current has a more northerly direction than 
the middle of it, this also should be guarded against. I con- 
ceive also, that the stream is broader in the parallel of Scilly, 
than farther south. And here we may remark, that those 
who, from a parallel south of Scilly, have been carried clear 
of it to the north, when approaching it, in the night, may 
esteem themselves fortunate that the current was so strong ; 
for had it been weaker, they might have been carried on the 
rocks. 

2d. A good observation of latitude, at noon, would be 
thought a sufficient warrant for running eastward, during a 
long night : yet as it may be possible to remain in the current, 
long enough to be carried from a parallel that may be deemed 
a very safe one, to that of the rocks of Scilly, in the course 
of such a night ; it would appear prudent, after experiencing 
a continuance of strong westerly gales in the Atlantic, and 
approaching the Channel with light southerly winds, either to 
make Ushant, or at all events to keep in the parallel of 48°, 
45', at the highest. If they keep in 49 0 , 30', they will expe- 
rience the whole effect of the current, in a position where 
they can least remedy the evil : but if in 48°, 45', they are 
assailed by the north-west current, they are still in a po- 
sition from whence a southerly wind will carry them into the 

MDCCXCIII. 2 D 


igH Mr. Rennbli/s Observations on a Current 

Channel. But all ships that cross the Atlantic, and are 
bound to the eastward of the Lizard, had better make Ushant, 
under the above circumstances, in times of peace. Or, at all 
events, why should they run in a parallel, in which they are 
likely to lose ground ? 

3d. Ships, bound to the westward, from the mouth of the 
Channel, with the wind in the south-west quarter, so that it 
may appear indifferent which tack they go on, should pre- 
fer the larboard tack ; as they will then have the benefit of 
the current. 

4th. I understand that the light house of Scilly is either 
removed, or to be removed, to the south-west part of the 
islands ; or of the high rocks. This is certainly a wise mea- 
sure ; as the light should be calculated more particularly for 
ships that have a long, than a short departure ; like those 
from any part of the European coasts, to the northward, or 
eastward. The light house ought also to be built very lofty. 
I am sorry to remark, that, as far as my observation has gone, 
this light has never appeared clear and bright, as a light to 
direct ships ought to do. 

5th. It would be worth the attention of government (in my 
humble opinion) to send a vessel with time keepers on board, 
in order to examine and note the soundings between the 
parallels of Scilly and Ushant, at least ; from the meridian of 
the Lizard point, as far west as the moderate depths extend ; I 
mean such as can be ascertained with exactness, in the ordi- 
nary method of sounding. I have reason to suppose that our 
chart of soundings is very bad ; and indeed, how can it be 
otherwise, considering the imperfect state of the art of ma- 
rine surveying, at the time when it was made ? A set of time 


*99 


that often prevails to the Westward o/'Scilly. 

keepers will effect more, in the course of a summer, in the 
hands of a skilful practitioner, than all the science of Dr. 
Halley, during a long life ; for who could place a single 
cast of soundings, in the open sea, without the aid of a time 
keeper ? The current in question, must have disturbed every 
operation of this kind. It should be the task of the person, 
so employed, to note all the varieties of bottom, as well as 
the depths ; the time of high and low water ; setting of the 
tides, and currents, &c. Such a survey, skilfully conducted, 
might enable mariners to supply the want of observations of 
latitude, and of longitude ; and, of course, to defy the current, 
as far as relates to its power of misleading them. 

6th. It is certain, that the current in question may be 
somewhat disturbed by, or rather will appear to be blended 
with, the tides, at the entrances of the British and St. George's 
Channels ; but it is obvious that the current will have the 
same effect, in setting a ship out of her course, as if no tide 
existed ; because, whatever effect one tide may have, the 
next will nearly do away. But there are two particulars, 
well worth ascertaining ; and these are, first, the point at 
which the two tides of St. George's, and of the British Chan- 
nel separate, on the west of Scilly. And secondly, what de- 
gree of northing one of the streams has, more than the other. 
Because a ship, in approaching Scilly, from the west, on a 
flood tide, and keeping in a parallel which may be to the 
north of the point of separation of the two tides, (and conse- 
quently in the tide stream of St. George’s Channel) may be 
thrown too far to the north ; although, had she been far 
enough to the west, to receive the effect of the next ebb, this 
temporary, and alternate derangement of the course, would 

2 D 2 


200 Mr. Renneli/s Observations on a Current, &c. 

have had no ill effect ; or even have been noticed. But 
admitting that a tide, with any degree of northing in it, does 
take place, a little to the west of Scilly ; this will furnish 
an additional reason for keeping in a southern parallel 
















/ 








V 




* 





\ 


Y 





C 201 3 


XVIII. Observations on the Planet Venus. By William 
Herschel, LL. D. F. R. S. 


Read June 13, 1793. 

The planet Venus is an object that has long engaged my 
particular attention. A series of observations upon it, which 
I began in April, 1777, has been continued down to the pre- 
sent time. 

My first view, when I engaged in the pursuit, was to as- 
certain the diurnal rotation of this planet ; which, from the 
contradictory accounts of Cassini and Bianchini, the former 
of which states it at 23 hours, while the latter makes it 
24 days, appeared to me to remain unknown, as to its real 
duration : for the observations of these gentlemen, how 
widely different soever with regard to time, can leave no 
doubt but that this planet actually has a motion on its axis. 

The next object was the atmosphere of Venus ; of the 
existence of which also, after a few months observations, I 
could not entertain the least doubt. 

The investigation of the real diameter, was the third ob- 
ject I had in view. 

To which may be added, in the last place, an attention to 
the construction of the planet, with regard to permanent ap- 
pearances ; such as might be occasioned by, or ascribed to, 
seas, continents, or mountains. 


202 


Dr. Herschel/s Observations 


The result of my observations would have been communi- 
cated long ago, if I had not still flattered myself with the 
hopes of some better success, concerning the diurnal motion 
of Venus ; which, on account of the density of the atmos- 
phere of this planet, has still eluded my constant attention, as 
far as concerns its period and direction. Even at this pre- 
sent time, I should hesitate to give the following extract 
from my journals, if it did not seem incumbent upon me to 
examine by what accident I came to overlook mountains in 
this planet, which are said to be “ of such enormous height , as 
to exceed four, Jive, and even six times the perpendicular elevation 
of Cimboraco, the highest of our mountains 1” * 

The same paper, which contains the lines I have quoted, 
gives us likewise many extraordinary relations, equally won- 
derful ; such as hints of the various and singular properties 
of the atmosphere of Saturn.-f A ragged margin in Venus, 
resembling the uneven border of the moon, as it appears to a 
power magnifying from i to 4.J One cusp of Venus appear- 
ing pointed, and the other blunt, owing to the shadow of 
some mountain. § Flat spherical forms conspicuous on Sa- 
turn. |! All which being things of which I have never taken 
any notice, it will not be amiss to shew, by what follows, that 
neither want of attention, nor a deficiency of instruments, 
could occasion my not perceiving these mountains of more than 
23 miles in height',** this jagged border of Venus ; and these flat 
spherical forms on Saturn. 

* See Phil. Trans, for 1792, Part II. page 337. f Ibidem, p. 309. J p. 310. 
§ p. 312. II P- 336. ** The height of Chimbo-ra9o, according to Mr. Con da- 

mine, is 3200 French toises; and the English mile, by Mr. De la La nde, measures 
830. If the mountains in Venus exceed Chimbo-rajo six times in perpendicular eleva- 
tion, they must be more than 23 miles in height. 


on the Planet Venus. 


203 


Indeed with regard to Saturn, I cannot hesitate a single 
moment to say, that, had any such things as flat spherical 
forms existed, they could not possibly have escaped my no- 
tice, in the numberless observations with 7, 10, 20, and 40- 
feet reflectors, which I have so often directed to that planet. 
However, if the gentleman who has seen the mountains in 
Venus, has made observations on flat spherical forms on Sa- 
turn, it is to be regretted that he has not attended to the re- 
volution of this planet on its axis, which could not remain an 
hour unknown to him when he saw these forms. 

Last night,* for instance, I saw two small dark spots on 
Jupiter ; I shall not call them flat spherical forms, because 
their flatness, as well as their sphericity, must be hypotheti- 
cal ; moreover, these two terms seem to me to contradict 
each other. These were evidently removed, in less than an 
hour, in such a manner as to point out, very nearly, the di- 
rection and quantity of the rotation of this planet. 

Before I remark on the rest of the extraordinary relations 
above-mentioned, I will give a short extract of my observa- 
tions on Venus, with such deductions as it seems to me that 
we are authorised to make from them. 

Observations. 

April 17, 1777. The disk of Venus was exceedingly well 
defined, dis inct, and bright, but no spot was visible by which 
I could judge of her diurnal motion. The same telescope 
shews the spots on Mars extremely well. 7-feet reflector. 

April 26, 1777. The disk well defined, and bright, but no 
spot. 10- feet reflector. 


May 31, 1793. 


204 


Dr. Herschel's Observations 


February 21, 1780. No spot on the disk of Venus; diameter 
i5",9, mean of three measures. 

May 2, 1780. No spot ; power 449; diameter 17", 2. 

May 28, 1780. No spot; power 268 and 449; diameter 
22", 8. 

May 29, 1780. I viewed Venus with a 20-feet Newtonian 
reflector ; power 447. The edge of the disk was so sharp and 
well defined, that there can be no wish to see it better. 
There was 110 spot of any kind. 

I could see no projections of any mountains, though the 
phase of Venus is now such as would be most favourable for 
shewing them. 

June 19, 1780. There is, on Venus, a bluish, darkish spot, 
&dc; and another, which is rather bright, red; they meet 
in an angle at c, the place of which is about one-third of the 
diameter of Venus from the cusp a. See Tab. XXII. fig. 1. 

June 21, 23, 24, 25, 2 6, 28, 29, 30, and July 3, 1780. Con- 
tinued observations were made upon these, and other faint 
spots, and drawings of them annexed. The instrument I 
used was a 20-feet Newtonian reflector, furnished with no 
less than five different object specula, some of which were in 
the highest perfection of figure and polish ; the power ge- 
nerally 300 and 450. But the result of them would not give 
me the time of the rotation of Venus. For the spots assumed 
often the appearances of optical deceptions, such as might 
arise from prismatic affections ; and I was always very un- 
willing to lay any stress upon the motion of spots, that 
either were extremely faint and changeable, or whose situa- 
tion could not be precisely ascertained. 

However, that Venus has a motion on an axis cannot be 


on the Planet Venus. 


•05 

doubted from these observations ; and that she has an atmo- 
sphere is as evident, from the changes I took notice of, which 
surely cannot be upon the solid body of the planet. 

Sept. 18, 1780. No spot on Venus; diameter 38", 4. 

Oct. 10, 1780. With a very perfect 7-feet speculum ; power 
227, 460, and 932. No spot visible ; diameter 41", 3. 

Oct. 11, 1780. No spot ; diameter 2 7 // ,8. 

Oct. 20, 21, 23, 1780. No spot visible. 

April 17, 1783. 10-feet reflector; power 324. I see some 
darkish spots on Venus. 7-feet reflector ; power 227. The 
same appearances; but in neither of the instruments are they 
determined enough to serve for the purpose of finding the 
rotation. 

May 21, 1783. 10-feet reflector ; a new speculum ; power 
250. 

7 h 30'. No spot visible. 

8 h 30'. There seems to be an ill defined spot. 

9 h 15'. No motion can be perceived that may be depended 
upon, though the figure seems rather advancing towards the 
centre. 

May 30, 31, and June 1, 6 , 1783. Spots were observed 
with 10 and 20-feet reflectors, and also motion perceived in 
them. Continued observations were recorded ; and a great 
many figures delineated. 

Dee. 3, 1783. With 460, and 932. No spot. No kind of pro- 
tuberance, or indenture in the line which terminates the illu- 
mination, that might denote a mountain. 

Feb. 13, 1785. No spot. A new 10-feet Newtonian reflector. 

April 8, 1788. No spot on Venus; but she is still at too 
great a distance for such observations. 

2 E . 


MDCCXCIII. 


sob* Dr. Herschel j s Observations 

Nov. 30, 178c). No satellite visible. If she has one, it must 
be less in appearance than a star of the 8th or 9th magni- 
tude ; power 300. 

Dec. 2, 1789. No spot ; power 157, 300, and 460. 

May 23, 1791. 40-feet reflector. The light of Venus is so 
brilliant that it becomes very uneasy for the eye to bear it 
long. There is no spot on the disk. 

I had prepared my apparatus for a regular succession of ob- 
servations with this instrument, having turned it towards the 
west, and put on the round-motion to keep the planet in 
view ; but found that the great advantage of this telescope, 
which is its superior light, was, on this occasion, not only un- 
necessary, but rather an inconvenience. 

Nov. 24, 1791. Correction of the clock, — 4 6", 7. 

I took measures of the diameter of Venus with the 20-feet 
reflector ; power 157. 

i2 h 18' 1st measure 45",486 
2d -46 ,142 

3 d 45 .514 

4th 45 ,814 

5 th 4 6 >°33 

6th 46 ,252 

Mean of the six measures 45",874 

I took five more, with a power of 300, the morning be- 
ing very fine and clear. 


on the Planet Venus. 


207 

i2 h 3 6' 1st measure 44", 885 
2d 45 ,705 

3 d 45 ,104 

4th ■ 45 ,322 

5th 45 ,842 


Mean of the five measures 45",372 

Mean of the two sets 45", 623 

These measures were taken with a speculum that has been 
lately re-polished, and therefore required new tables for 
casting them up. Such tables were made by the following 
transits. 

Nov. 25, 1791. Transits of equatorial stars, taken to deter- 
mine the value of the micrometer, which is divided into re- 
volutions of sixty parts each. 

First set, 23", o 23,0 23,0 23,0 23,2 23,1 23,1 23,0 23,1 
23,1 = 23", 06 = 21 revolutions; correction -f- 7,2 parts, for 
zero and concave wires. 

Second set, 16", 8 16,6 16,4 16,5 16,7 16,6 16,5 16,8 16,4 
16,5= 16,58 = 15 revolutions 1,3 parts. Correction 7,2. 

By the first set, 1 part = o ", 272964 

Second set - - 273748 


Mean of the two sets o", 2 73356 
In the first set, the micrometer was opened to 21 revolu- 
tions ; and ten equatorial stars were observed to pass from 
one wire to the other. The opening was afterwards changed, 
and ten other stars were again observed to pass over the 
wires ; after which the micrometer was read off, and found to 
be 15 revolutions and 1,3 parts. 

2 E 2 


208 


Dr. Herschei/s Observations 


Feb. 4, 1793. Correction of the clock, — 1' 28", o. 

2 h 55'. 7-feet reflector ; power 172. The air is very clear* 
and I see Venus very well defined ; but cannot perceive any 
inequality on the edge of the planet that might denote a 
mountain ; though the situation is favourable, being a little 
more enlightened than what we may call her last quarter. 
With 215 , 1 had a very distinct view for a long time; but can- 
not perceive any inequality on the line which divides light 
from darkness. 

With 287 , 1 perceive no mountains : with 430, very distinct, 
I perceive no mountains. The terminating line is not so 
sharply defined as the circumference; but no inequality is 
visible. 

With the same power, I see on Saturn, the equatorial belt, 
the shadow of the ring on Saturn, the shadow of Saturn on 
the ring, the division of the ring, &c. 

I do not find any spot on Venus ; so that there is no possi- 
bility to assign its diurnal motion. 

March 3, 1793. Correction of the clock, — 2' o", 6 . 

6 h 30'. 7-feet reflector ; I observed Venus with many 
powers, but could perceive no spot by which its diurnal mo- 
tion might be ascertained. 

April 3, 1793. Correction of the clock, — 2' 43", 9. 

q h 9'. 7-feet reflector; power 215. The evening remark- 
ably fine. There is no spot upon the disk of Venus, by which 
its rotation might be ascertained. The horns are equally 
sharp. There is nothing that has the appearance of a moun- 
tain, like what we see in the moon. With 287, very well de- 
fined, appearances are the same. With 430, not the least ap- 
pearance of any mountains. 


on the Planet Venus. 


20 9 


April 4, 1793. Correction of the clock, — 2' 45", 3. 

9 h 8'. There is no spot upon the disk of Venus. The horns 
are perfectly alike. 

Not the least appearance like the mountains of the moon. 
With 287, and 430, very distinct. 

April 5, 1793. Correction of the clock, — 2' 46^,7. 

8 h 25'. 7-feet reflector; power 215, 287, and 430. There 
are no spots upon Venus, by which its diurnal motion could 
be ascertained. The horns are exactly alike ; and no ine- 
quality, like the mountains of the moon, is visible. 

April 6, 1793. Correction of the clock, — 2' 48",!. 

9 h 29'. With the 7-feet reflector ; power 430. There is no 
kind of spot visible in any part of the disk. The two horns 
are exactly alike ; and no appearance of mountains can be 
perceived. 

April 7, 1793. Correction of the clock, — 2' 4 9", 6. 

9 h 8\ With the 7- feet reflector ; power 215, 287, 430, and 
860. I can see no spot upon the disk. Both horns are per- 
fectly alike. Nothing resembling the mountains upon the moon 
can be perceived. I see it beautifully well, and sharply defined. 

April 8,-1793. Correction of the clock, — 2' 51", o. 

9 h 2'. With the 10-feet reflector ; power 300, and 400 
There is no spot upon Venus. The shape of the two horns is 
perfectly alike, and no appearance of mountains can be per- 
ceived. The illumination of the horns is also perfectly alike. 

April 9, 1793. Correction of the clock, — 2' 52", 1. 

8 h 45'. With the 10-feet reflector ; power 300. No spot 
upon Venus. Both horns perfectly alike. No appearance of 
mountains. 

The light of Venus is brighter all around the limb, than on 


210 


Dr. Herschel's Observations 


that part which divides the enlightened, from the unenlight- 
ened part of the disk. With 400, appearances are the same. 

g h 1 6'. The bright part, on the limb of Venus, is like a 
bright bead, of nearly an equal breadth all around. 

April ib, 1703. Correction of the clock, — 2' 59", 5. 

1C)h o ' • 7-feet reflector, with different powers. No spot 
upon the disk. No mountains visible. Both horns alike. 

A luminous margin, as usual, all around the limb. 

April 20, 1793. Correction of the clock, — 3' 3", 8. 
io h o'. 7-feet reflector ; power 172, 213, 287, 430, and 
8bo. No spot upon the disk. Both horns exactly alike. Not 
the least appearance of any mountains. 

With 287, there is a narrow luminous border all around the 
limb, and the light afterwards diminishes pretty suddenly, and 
suffers no considerable diminution as we go towards the line 
which terminates the enlightened part of the disk. It is how- 
ever less bright near the terminating line than farther from it. 
With powers lower than 287, the narrow luminous border 
cannot be so well distinguished. 

April 22, 1793. Correction of the clock, — 3' 5", 9. 

9 h 30'. 7-feet reflector ; power 430. Very distinct. No spot. 
No appearance of mountains. Both horns perfectly alike. 

With 860, 1290, and 1720, not the least appearance of 
mountains. Even the last power is considerably distinct. 

io h 20'. With 430, the luminous margin, compared to the 
light adjoining to it, may be expressed by, suddenly much 
brighter all around the limb. 

April 28, 1793. Correction of the clock, — 3' 12", 3. 
i2 h o'. 7-feet reflector ; power 215. No spot. Both horns 
perfectly alike. No appearance of mountains. 


on the Planet Venus. 


211 


April 2 9, 1 793. Correction of the clock, — 3' 13", 4. 
io h 30'. 7-feet reflector ; power 215. No spot. Both horns 
perfectly alike. Not the least appearance of any mountains. 

With 287 and 430. Both horns equally sharp : no moun- 
tains visible. 

May 1, 1793. Correction of the clock, — 3' 15", 5. 
io h 45'. With the 10-feet reflector ; power 300. No spot. 
Both horns perfectly alike, and very sharp. Not the least ap- 
pearance of any mountains. 

With 600, very distinct. Both horns extremely sharp, and 
alike, b o mountains. 

With 400, the same appearances. 

May 5, 1793. Correction of the clock, — 3' 19", 8. 
n h 27'. 7-feet reflector; power 215, 287, and 430. Both 
horns perfectly alike. No spot. Not the least appearance of 
any mountains. 

May 12, 1793. Correction of the clock, — 3' 27",%. 
n h io'. 7-feet reflector ; power 215. Beautifully distinct. 
No spot visible ; indeed the crescent is so slender, that we 
cannot expect to see any spots upon the disk. 

Not the least appearance of any mountains, or inequality 
on the border. 

The slender part of the crescent appears often knotty, but 
this is evidently a deception arising from undulations in the 
air ; for, with proper attention, the knots may be perceived to 
change place. Little scratches in the great, or small specu- 
lum, may also occasion seeming irregularities ; but, with pro- 
per attention, all such deceptions may be easily detected. Both 
horns perfectly alike. 


212 


Dr. Herschel‘s Observations 


With 287, 430, and 860, all that has been mentioned be- 
fore is perfectly verified, and confirmed. 

n h 43'. I tried also the lower powers of 172, and 115; 
but they are inferior, in effect, to 215, 287, and 430 ; and not 
adequate to the delicacy and power required in such obser- 
vations. 

I have often taken notice, and again this evening, that the 
illuminated part of Venus is more than a semi-circle. Whe- 
ther the excess of the sun's diameter alone will account for 
this, or how far we are to take the twilight of the atmosphere 
of Venus into consideration, I have hitherto deferred investi- 
gating, as my disk-micrometer wants a moveable parallel, in 
order to be adjustable, by observation, to the quantity of the 
horns which is enlightened beyond an hemisphere. 

May 13, 1793. Correction of the clock, — 3' 28", 4. 
n h 45'. 7-feet reflector; power 115, 172, 215, 287, and 
430. Both horns perfectly alike. No appearance of moun- 
tains. 

The points of the horns appear more blunt than they were 
last night, and are not drawn out to so slender a point ; but 
this is evidently a deception, owing to the indifference of the 
night ; for great sharpness, and distinct vision, are wanting 
in every other object I am looking at. 

May 18. 1793. Correction of the clock, — 3' 33 ",7. 
i2 h 28'. 7-feet reflector ; power 287. Both horns per- 
fectly alike. No appearance of mountains. No spot. But, at 
the present altitude of Venus, it is impossible to make any ob- 
servations that require delicacy, and demand very distinct vi- 
sion with high powers. 


on the Planet Venus. 


213 


May 19, 1793. Correction of the clock, — 3' 34", 7. 

n h 45'. 7-feet reflector ; power 287. Both horns perfectly 
alike, in shape and illumination. Not the least appearance of 
any mountains. The horns are exceedingly slender. 

i2 h o'. I do not see any diminution of light on the edge of 
the horns, but what may be accounted for from their slender- 
ness ; being brought to very fine points, that lose themselves 
by their minu eness. 

I saw it in great perfection, with a newly polished, plain 
speculum, which excels my former one in sharpness. 

May 20, 1793. Correction of the clock, — 3' 35",8. 

i2 h 20'. No spot or unevenness in the light of Venus upon 
either cusp, or in any other part, that could in the least make 
me suspect a mountain. 

I measured the diameter of Venus, and projection of the 
cusps beyond an hemisphere, by my disk-micrometer. This 
was not done by an illumination, as described in the appara- 
tus, (Phil. Trans. Vol. LXXIII. p. 4.) when I used it for a 
nocturnal planet ; for, day-light being sufficiently strong, 
there was no occasion to light the lamps. On the measuring 
disk were drawn concentric circles ; and also a diameter, hav- 
ing several lines parallel to it, in one of the semicircles. If 
there had been time, I should have prepared a straight edge, he, 
moveable parallel to the diameter a d. See Tab. XXII. fig. 2. 

First measure, with the double eye-glass ; power about 30. 
Diameter of Venus 2390. Projection 500. But the power is 
too low to be accurate. 

Second measure ; power 215. Diameter of Venus 4800. Pro- 
jection 620. Here the projection is probably as much too small 
as the former was too large ; but the planet is too low for re- 

2 F 


MDCCXCII I. 


214 


Dr. Herschei/s Observations 


peating the measures. A mean of both may, perhaps, not be 
far from the truth ; which gives, diameter 3595 ; projection 
560. 

Here 1797,5 being radius, and 560 sine, we find the angle 
a c b, or d c e, equal to 18 0 9' 8", 2, 

A few very evident results may be drawn from the forego- 
ing observations. 

With regard to the rotation of Venus on an axis, it ap- 
pears that we may be assured of this planet's having a diurnal 
motion, and though the real time of it is still subject to con- 
siderable doubts, it can hardly be so slow as 24 days. Its di- 
rection, or rather the position of the axis of Venus, is involved 
in still greater uncertainty. 

The atmosphere of Venus is probably very considerable ; 
which appears not only from the changes that have been ob- 
served in the faint spots on its surface, but may also be inferred 
from the illumination of the cusps, when this planet is near 
its inferior conjunction ; where the enlightened ends of the 
horns reach far beyond a semicircle. I must here take notice, 
that the author we have before quoted on this subject, has the 
merit of being the first who has pointed out this inference, 
but he has overlooked the penumbra arising from the diame- 
ter of the sun ; * which has certainly a considerable share in 

* He mentions it upon another occasion, and says in a note, p. 313, that “ this whole 
penumbra, which, according to the greatest apparent diameter of Venus, extends 
from 59 to 60", (for what reason he fixes upon these quantities does not appear) 
“ measures, in the direction perpendicular to the line of the cusps, only o" 36.” But 
if, according to him, the apparent diameter of the sun be 44', (which is less than it 
ought to be) the penumbra must certainly extend likewise upon the surface of Venus 


on the Planet Venus. 


215 


the effect of the extended illumination, and in his angle of 
15° 19' will amount to more than two degrees and a third. 
His measures are also defective ; as probably the mirror of his 
7-feet reflector, which was a very excellent one, was by that 
time considerably tarnished, and had lost much of the light 
necessary to shew the extent of the cusps in their full bril- 
liancy. 

I do not give the calculations I have made of the extent of 
the twilight of Venus, because my measures were not so sa- 
tisfactory to myself as I wish them to be ; nor so near the 
conjunction as we may hereafter obtain them ; neither were 
they sufficiently repeated. My computations, however, when 
compared to those given in the paper on the atmosphere of 
Venus, shew sufficiently that it is of much greater extent, or 
refractive power, than has been computed in that paper. 
Those calculations indeed are so full of inaccuracies, that it 
would be necessary to go over them again, in order to com- 
pare them strictly with my own, for which at present there is 
no leisure. 

I ought also to take notice here, that the same author, it 
seems, has taken measures of the horns of Venus by an in- 
strument, which, in his publications, he calls a projection table , 
and describes as his own * ; of which, however, those who do 
not know its construction may have a very perfect idea, when 
they read the descriptions of my lamp, disk, and periphery 

over 44 of a great circle ; and, in the situation which he mentions, that is, perpendi- 
cular to the line of the cusps at the time of the greatest elongation, and when the ap- 
parent diameter of Venus is 60", (as he makes it) it must measure o",3§4. 

* See Beitrdge zu den neuesten astr onomiscben Entdeckungen, p. 210. And Seleno- 
topographische Fragmente, p. 63. 


2 F 2 


2i 6 Dr. Herschei/s Observations 

micrometers, joined to what I have mentioned above, of 
using the disk-micrometer without lamps when day-light is 
sufficiently strong ; or even with an illumination in front, 
where the object is bright enough to allow of it, such as the 
moon, &c. 

I remember drawing the picture of a cottage by it, in the 
year 1776, which was at three or four miles distance; and 
going afterwards to compare the parts of it with the building, 
found them very justly delineated. 

I have also many times had the honour of shewing my 
friends the accuracy of the method of applying one eye to 
the telescope, and the other to the projected picture of the 
object in view ; by desiring them to make two points, with a 
pin, upon a card fixed up at a convenient place, where it 
might be viewed in my telescope ; and this being done, I 
took the distance of these points from the picture I saw pro- 
jected, in a pair of proportional compasses, one side of which 
was to the other as the distance of the object, divided by the 
distance of the image, to the magnifying power of the te- 
lescope ; and giving the compasses to my friends, they gene- 
rally found that the proportional ends of them exactly fitted 
the points they had made on the card. All which experiments 
are only so many different ways of using the lamp-micro- 
meter. 

As to the mountains in Venus, I may venture to say that 
no eye, which is not considerably better than mine, or as- 
sisted by much better instruments, will ever get a sight of 
them ; though, from the analogy that obtains between the 
only two planetary globes we can compare, (the moon and 
the earth) there is little doubt but that this planet also has 


on the Planet Venus. 


217 

inequalities on its surface, which may be, for what we can say 
to the contrary, very considerable. 

The real diameter of Venus, I should think, may be in- 
ferred with great confidence, from the measures I took with 
the 20-feet reflector, in the morning of the 24th of Novem- 
ber, 1791; which, when reduced to the mean distance of the 
earth, give 18", 79 for the apparent diameter of this planet. 

This result is rather remarkable, as it seems to prove that 
Venus is a little larger than the earth, instead of being a little 
less, as has been supposed ; yet, upon the nicest scrutiny, I 
cannot find fault with the measures. The planet was put be- 
tween the two wires of the micrometer, which were outward 
tangents ; and they were, after each measure, shut, so as to 
meet with the same edge, and in the same place where the 
planet was measured. In this situation the proper deduction, 
for not being central measures, was pointed out by the index 
plate. The transits of the 25th were corrected for a small con- 
cavity of the wires, which being pretty thick and stubborn, 
were not strained sufficiently to make them quite straight, the 
amount of which was also ascertained by an examination of 
the division where the wires closed at the ends, and where 
they closed in the centre. The zero was, with equal precau- 
tion, referred to a point at an equal distance from the contact 
of the wires on each side ; for they are at liberty to pass over 
each other, without occasioning any derangement. The shake , 
or play, of the screw is less than 3-tenths of a division. 

The two planets, however, are so nearly of an equal size, 
that it would be necessary to repeat our measures of the dia- 
meter of Venus, in the most favourable circumstances, and 


2l8 


Dr. Herschei/s Observations 


with micrometers adjusted to the utmost degree of precision 
in order to decide with perfect confidence that she is, as ap- 
pears most likely, larger than the earth. 

The remarkable phaenomenon of the bright margin of Ve- 
nus, I find, has not been noticed by the author we have re- 
ferred to : on the contrary, it is said, page 310, “ this light 
appears strongest at the outward limb ab c, from whence it de- 
creases gradually, and in a regular progression, towards the in- 
terior edge, or terminator.” But the luminous border, as I 
have described it, in the observations of the 9th, 16th, 20th, 
and 2 2d of April, does not in the least agree with the above 
representation. 

With regard to the cause of this appearance, I believe 
that I may venture to ascribe it to the atmosphere of Venus, 
which, like our own, is probably replete with matter that 
reflects and refracts light copiously in all directions. There- 
fore on the border, where we have an oblique view of it, 
there will of consequence be an increase of this luminous ap- 
pearance. 1 suppose the bright belts, and polar regions of 
Jupiter, for instance, which have a greater light than the 
faint streaks, or yellow belts, on that planet, to be the parts 
where its atmosphere is most filled with clouds, while the 
latter are probably those regions which are free from them, 
and admit the sun to shine on the planet ; by which means 
we have the reflection of the real surface, which 1 take to be 
generally less luminous. 

If this conjecture be well founded, we see the reason why 
spots on Venus are so seldom to be perceived. For, this 
planet having a dense atmosphere, its real surface will com- 


Philos. Tracis. MDCCXCITL. Tab. XXII p.2iS. 





on the Planet Venus. 


21 9 


monly be enveloped by it, so as not to present us with any 
variety of appearances. This also points out the reason why 
the spots, when any such there are, appear generally of a 
darker colour than the rest of the body. 


£ 220 ] 


XIX. Abstract of a Register of the Barometer, Thermometer , and 
Rain, at Lyndon, in Rutland. By Thomas Barker, Esq. ; with the 
Rain in Surrey and Hampshire, for the Tear 1792 ; and a Compari- 
son of wet Seasons. Communicated by Thomas White, Esq. F. R. S. 


Read June 20, 1793. 




Barometer. 

Thermometer. 

Rain. 






In the House. 

Abroad. 


Surrey. 

Hampshire. 












Lyndon. 

South 

Sel- 

bourn. 




Highest. 

Lowest. 

Mean. 

High. 

Low. 

Mean. 

High. 

Low. 

Mean. 


Lam- 

beth. 

Fyfield. 



Inches. 

Inches. 

Inches. 

O 

O 


0 

O 

O 

Inches. 

Inches. 

Inches. 

Inches. 

Jan. 

Morn. 

Aftern. 

29,92 

28,47 

29,18 

47 2 
49 

3° 

3°f 

39 

39i 

46! 

54 

16 

25 

34? 

2,097 

2,51 

6,07 

4*47 

Feb. 

Morn. 

Aftern. 

94 

29,04 

48 

Mk 

49 

32 

34 

41 

42 

4 7k 
55 

# 

35 

4 2 Jr 

0,712 

O 5 

1,68 

1, 6 

Mar. 

Morn. 

Aftern. 

30,00 

28,53 

26 

5° 

5i 

35 

35§ 

44 

45 

481 

57 

25 \ 
3°i 

39 
47 £• 

1,096 

2,13 

6,70 

2,92 

Apr, 

Morn. 

Aftern. 

29,85 

7 2 

42 

60 

62 

43z 

44 

5 1 

53 

56 

7i 

3 6 l 

39 

46 

57 

4,042 

2, 4 

4,08 

2, 9 

May 

Morn. 

Aftern. 

9 1 

77 

49 

58 \ 
62 

45 

46 

5°i 

53 

58 

68 

3<4 

45 

47 5; 
57 

1 ,660 

049 

3,00 

2,51 

June 

Morn . 
Aftern. 

88 

97 

46 

6 3 

67 

5° 

53 

54z 

57 

6 4f 

77i 

47 

49 

53 

62J 

4>°43 

D45 

2,78 

307 

July 

Morn. 

Aftern. 

7 1 

290 3 

4i 

6 5 

68 

53 

57f 

59? 

61 

66i 

78 

52 

57t 

57y 

67I 

3> 6 74 

3 >98 

5,16 

3,81 

Aug. 

Morn. 

Aftern. 

83 

28,89 

48 

69 

73 

57 

59f 

62I 

65 

6 7 f 

79s- 

5° 

61 

58J 

70 

2,861 

2,86 

4,25 

2,52 

Sep. 

Morn. 

Aftern. 

85 

57 

3° 

*4 

6 3l 

48| 

50 

55 

56 

60 

68f 

44 

48 

5° 

58 

3>977 

2,66 

5’53 

3>93 

Oct. 

Morn. 

Aftern. 

97 

72 

34 

58 

59 

4 6 
46 

49 

5°f 

57 

66 

35 

46 

34 

37i 

45i 

52 

D75 6 


5>55 

4, 6 

Nov. 

Morn. 

Aftern. 

9 1 

78 

5 2 

51-1 

53 

4°2 

39l 

46 

4 6 r 

5°f 

56 

42J 

47 

0,761 


1,65 

90 

Dec. 

Morn. 

Aftern. 

85 

5° 

31 

48 

48J 

3 6 

3 6 

4 1 

42 

52 

54 

29 
3 1 

39 

44 

2,723 


2,1 1 

1,40 









■1— 



29,402 


48,56 

32,84 


221 


Mr. Barker's Register, &c. 

The winter was a severe one ; there was a sharp frost every 
month from December to March, chiefly between the full and 
the new moons, and the intervals were often stormy and wet ; 
but those in February, both at the middle and latter end of 
the month, were milder, and less wet. The beginning of 
March continued mild, with frequent though small rains ; 
then followed as sharp a frost, for a week, as any in the win- 
ter. After that stormy weather into April, but warm and 
growing ; till a violent thunder storm toward Stamford the 
13th, and two days continued rain here, and in most other 
places, about the 18th, renewed the wet season ; which lasted 
all summer, and was perhaps wetter in many places than 
here, for we had no heavy thunder storms all the summer, as 
they had in some parts. Whenever there was thunder this 
year, it was almost always cold after it, and often cold weather 
without it ; very little sunshine, and many sharp frosty 
mornings both in May and June, which cut off the apples 
after they appeared to be set. The greatest rains this sum- 
mer were after the middle of April ; before the middle of May ; 
about the 8th of June; the 21st of July; the 18th of August; 
and 14th of September : those in April, June, and July, made 
floods, the two latter of which did great damage to the mea- 
dow hay ; and there were frequent, sometimes almost daily, 
lesser rains. The intervals of fair and fine weather were short, 
and not many, and those not always warm ; the beginning of 
May, and about the 21st; the beginning and end of June; the 
beginning of July; and, what was the finest time this summer, 
the first half of August. During this, in general so very wet a 
season, the hay and harvest were got in, and, where they 
were not flooded, I think with less damage than might have 

MDCCXCIII. 2 G 


222 Mr. Barker’s Register, &c. 

been expected. The latter hay was got up during the fine 
time in August ; some of the harvest in a tolerable time the 
beginning of September ; and what was delayed by the al- 
most daily rains for two-thirds of September, was finished in 
a fine time the beginning of October ; the crop of wheat was 
tolerable well, but barley, oats, and peas, were dear. 

This year was the wettest since 1782, which, with 1774, 
and some others, exceeded it ; and this, like those two years, 
began to grow less wet the beginning of October. Yet the 
frequent rains after that, though less in quantity, kept the 
ground from drying, which was already too wet, and the roads 
continued uncommonly torn up all winter ; and December, 
being wetter, increased it. The last six weeks of the year 
were in general dark and cloudy, or misty ; very little sun, 
and not much frost, and so far seems to promise an open 
winter ; but December was a stormy time ; several great 
ones, and some great rains and floods. 


Mr. Barker’s Register , &c. 

A Comparison of wet Seasons. 
Twelve Months. 


223 


No. I. 



1774 - 


1782. 


1792. 

- 


Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

January 

3 > 3 o8 


2,333 

2,969 

2,097 


February 

1,946 

5,254 

0,636 

0,712 

2,809 

March 

2,728 

7,982 

1,923 

4,892 

1,096 

3,905 

April 

1 > 5 2 3 

9,505 

6,125 

I 1,017 

4,042 

7-947 

May 

3,142 

12,647 

5,722 

16,739 

I,66o 

9,607 

June 

2,483 

15,130 

1,295 

18,034 

4,043 

13,650 

July 

3,227 

i g ,357 

2,697 

20,731 

3,674 

17,324 

August 

3 > 9 IQ 

22,267 

3 ,H 4 

23, 8 45 

2,86l 

20,185 

Septem. 

8,000 

30,267 

5,151 

28,996 

3-977 

24,162 

October 

1,156 

31,423 

1,502 

30,498 

1,756 

25,91 8 

Novem. 

i> 53 ° 

32,953 

1,074 

31,572 

0,761 

26,679 

Decern . 

2,282 

35-235 

0,517 

32,089 

2,723 

29,402 

Three 

1773 
1 775 

years 

29,376 

31,699 

96,310 


No. II. 


Oct. 3, 1773 to 

Dec. 1774 to 

Oct. 1791 to 

Feb. 1 

763 to 

1768. 

Oct. 2, 

1774 - 

Nov. 

1775 - 

Sept. 

1792. 

Jan. 

1764. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 

Oct. 3 

2,615 

Dec. 

2,282 

Oct. 

3,319 

Feb. 

2,882 

Jan. 

2,834 

Nov. 

3,605 

[an. 

1,973 

Nov. 

4,231 

Mar. 

0,919 

Feb. 

3,062 

Dec. 

2,897 

Feb. 

2,522 

Dec. 

1,150 

April 

0,692 

March 

0,391 

Jan. 

3,308 

Mar. 

1,728 

Jan. 

2,097 

May 

2,304 

April 

2,023 

Feb. 

1,946 

April 

1,035 

Feb. 

0,712 

June 

2,420 

May 

1 ,622 

March 

2,728 

May 

0,900 

March 

1,096 

July 

5,657 

June 

4,521 

April 

1,523 

J une 

0,887 

April 

4,042 

Aug. 

2,929 

July 

2,402 

May 

3.I42 

July 

4,078 

May 

I,66o 

Sept. 

3,307 

Aug. 

1,720 

June 

2,483 

Aug. 

4,760 

June 

4>°43 

Oct. 

I,6o6 

Sept. 

3,025 

July 

3,227 

Sep. 

5,670 

July 

3, 6 74 

Nov. 

1,894 

Oct. 

3 ,H 9 

August 

3,910 

Oct. 

3,480; Aug. 

2,861 

Dec. 

3,525 

Nov. 

4,040 

Septem. 
Oct. 1 & 2 

8,000 

0 , 34 ° 

Nov. 

3,570 

Sept. 

3-977 

Jan. 

3,984 

Dec. 

2,146 


32,885 


32,862 


32,125 


30,905 










39,724 










2 G 2 


224 


Mr. Barker's Register , &c. 

No. III. 

Three years. 



May 9, 1773, to May 8, 

776. 

17 months.. — May9, 
1773, to Oct. 8, 1774. 

1 773 * 

1774 - 

1 775 • 

! 1776. 

1 773 • 

1774. 


Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Inches. 

Jan. 


3 ’ 3°8 

1 ’97 3 

2,511 


3.308 

Feb. 


1,946 

2,522 

3 > 1 95 


1,946 

March 


2,728 

1,728 

1,518 


2,728 

April 


i, 5 2 3 

1,035 

0,887 


0523 

May 

6,770 

3 A 4 2 

0,900 

0,860 

6,770 

3,142 

June 

2,389 

2,483 

0,887 


2,389 

2,483 

July 

0077 

3,227 

4,078 


I ’°77 

3,227 

August 

3 ’379 

3,910 

4,760 


3.379 

3,91° 

Septem. 

2,812 

8,000 

5,670 


2,812 

8,000 

October 

2,621 

1,156 

3,480 


2,62 1 

0,460 

Novem. 

3,605 

*, 53 ° 

3 , 57 ° 


3,605 


Decern. 

2,897 

2,282 

1,096 


2,897 



2 5 > 55 ° 

35’ 2 35 

31,699 

8 ’ 97 I : 

25,550 

30,727 



Three years time 

101,455 I 


56,277 


No. IV. 

Nine months. 


Jan 

. 6 , to 

Jul. 

1775 to 

Jan. 1782 

May, 1773 

May 

, 1763 

April, 1768 

Jan. 1792 

Oc. 6, 1774. 

Mar, 1776. 

to Sept. 

to Jan. 1774. 

to Jai 

1. 1764. 

to Dec. 

to Sept. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 

Jan. 

3 > 3 ° 8 

Jul. 

4,078 

Jan. 

2,333 

May 

6,843 

May 

2,304 

Aor. 

2,023 

Jan. 

2,097 

Feb. 

1,946 

Aug 

4,760 

Feb. 

0,636 

June 

2,389 

June 

2,426 

May 

1 ,622 

Feb. 

0,712 

Mar. 

2,728 

Sep. 

5,670 

Mar. 

1,923 

J ul y 

1,077 

July 

5,657 

June 

4,521 

Mar. 

1,096 

Apr. 

0523 

Oct. 

Nov. 

3.480 

Apr. 

6,125 

Aug 

3,379 

Aug 

2,929 

juty 

2,3.02 

Apr. 

4,042 

May 

3 .H 2 

3.570 

May 

5,722 

Sep. 

2,812 

Sep. 

3,307 

Aug 

1,720 

May 

I,66o 

June 

2,483 

Dec. 

1,096 

June 

1,295 

Oct. 

2,62 I 

Oct. 

1,606 

Sep. 

3,025 

June 

4,043 

July 

3.227 

Jan. 

2,5 I 1 

July 

2,697 

Nov. 

3,605 

Nov. 

1,894 

Oct. 

3 119 

July 

3,674 

Au. 

3 . 9 10 

Feb. 

3.195 

Aug 

3.114 

Dec. 

2,897 

Dec. 

3,525 

Nov. 

4,040 

Aug 

2,861 

Sep. 

Oct. 

8,000 

0,460 

Mar. 

1,518 

Sep. 

5.151 

Jan. 

3,308 

Jan. 

3,984 

Dec. 

2,146 

Sep. 

3-977 


29,878 


28,996 


28,931 


27,632 


24,618 


24,162 











30,727 














Mr . Barker's Register , 


22 5 


No. V. 

Six months. 


April 12 

^4 

oo 

tsi 

July to Dec. 

April to Sept. 

April to Sept. 

to Oct. ii. 

1775 - 

> 774 - 

1792. 


Inches. 


Inches. 


Inches. 


Inches. 

April 12 

5,375 

July 

4,078 

April 

I ’ 5 Z 3 

April 

4,042 

May 

5,722 

tug. 

4,700 May 

3 .H 2 

May 

I,66o 

June 

I >-95 

cept. 

5,670 

June 

2,483 

J une 

4,043 

July 

2,697 

Oct. 

3,480 

July 

3> 22 7 

July 

3> 6 74 

August 


Nov. 

3.570 

Aug. 

3,910 

Aug. 

2,86l 

Septem. 

5,15* 

Dec. 

1,096 

Sept. 

8,000 

Sept. 

3,977 

Oct. to 1 1 

0,950 










22,654 


22,285 


20,25 7 


24,304 








No. VI. 

Three months. 


July 3, 1774, 
to Oct. 2. 

1775 - 

N 

OO 

1770. 

July 3 

Inches. 

3, 22 7 

July 

Inches. 

4,078 

Mar. 

Inches. 

1,923 

Oct. 

Inches. 

3 ,» *4 

August 

3 > 9 ID 

Aug. 

4,760 

Apr. 

6,125 

Nov. 

7,818 

Septemb. 

8,000 

Sept. 

5,670 

May 

5,722 

Dec. 

2,613 

Oct. 1 Sc 2 

0 , 34 ° 

15,477 


OO 

0 


I 3 » 77 ° 


1 3,545 


1763. 

1737 - 

^4 

OO 

May 25, 1792, 
to Aug. 24. 

July 

Inches. 

5, b 57 

Aug. 

Inches. 

6,300 

May 

Inches. 

2,890 

May 25 

Inches. 

0,770 

Aug. 

2,929 

Sept. 

3,465 

June 

3,810 

June 

4,043 

Sept. 

3,307 

Oct. 

2,025 

July 

5,080 

July 

3,674 


11,893 


11 , 79 ° 


1 1,780 

Au. to 24 

2,511 

10,998 


226 


Mr. Barker's Register , &c. 


No. VII. 


No. VIII. 


One month. 


Abstract. 



Inches. 

1774 September 3 

7>93° 

to Oct. 2 

0,34° 


8,270 

1770 November 6 

7,818 

to Dec. 5 

0,410 


8,228 

1773 May - - 

6,843 

1736 July 

6,550 

•737 August 

6,300 

1782 April 

6,125 

1757 August 

6,057 

1782 May 

5,722 

1775 September 

5,670 

1763 July - - 

5,657 

•743 Juty - - 

5,230 

1776 August 

5,200 

1782 September 

5,151 

1792 August 16 

2,762 

to Sept. 15 

2,346 


5,108 


Inches. 


Three years time 
Three calendar years, 1773, 
1774, and 1775 - 

Seventeen months 
Twelve months 
Nine months 
Six months 
Three months - 
One month 


IOI »455 

96,310 

56,277 

39>724 

30,727 

24,304 

• 5»477 

8,270 


The year 1792 was a very wet one, and by many ima- 
gined to exceed all others, but that does not appear to be 
fact ; the wet of last year is fresh in memory, that of 
former years is more forgotten. It might seem the wetter, 
because the autumn of 1791 was wet, so that there was a 
long continuance of it ; and perhaps there might be more 
rain in some other places than here, as we had no great thun- 
der storms all the summer at this place, which they had in 
several parts, some not many miles off. The wettest years 


227 


Mr. Barker’s Register , &c. 

here were about 1774 and 1782, which I have therefore com- 
pared with last year, in No. I. where I have set down the 
whole rain, and cast up the sum, from January the first, to 
the end of every month, in each year : and it appears, that to 
the end of January, to the end of February, and of March, the 
wettest was 1774, the next 1782, and 1792 was less wet than 
either of them. The very wet April and May in 1782 altered 
the order of them ; and to the end of April, of May, of June, 
of July, and of August, the wettest was 1782 ; the next 1774; 
and the last 1792. September, 1774, that wettest of all months 
in fifty-seven years, altered the order again to 1774, 1782, 
1792 ; and it continued so to the end of the year. In No. II. 
I have given some of the greatest twelve months, whether be- 
ginning with January or not ; and the greatest 365 days is 
from October 3, 1773 to October 2, 1774, which is 39,724 
inches ; and all that I have here given exceed 1792. In No. 
III. is the greatest three years, from May 9, 1773 to May 8, 
1776, which is 101,455 inches; and the greatest seventeen 
months, from May 9, 1773 to October 8, 1774, is 56,277 
inches. In No. IV. are the greatest nine months, January 6 
to Octoberb, 1774, 30,727 inches; and several others, to 1792, 
24,162 inches. In No. V. are several of the greatest six months, 
from 1774, 24,304 inches, to 1792, 20,257 inches. In No. VI. 
are several of the greatest three months, from 15,477 inches 
in 1774, to 10,998 inches in 1792. The greatest month last 
year was, from August 16 to September 15, 5,108 inches, 
but I have had thirteen greater; the most of all was in 1774, 
8,270 inches; the rest are set down in order in No. VII.; 
and the last is that in 1792. Lastly, in No. VIII. I have set 
down together the wettest times in all the several cases. 


228 Mr. Barker's Register , &c . 

At Selbourn, between Alton and Petersfield, in Hampshire, 
which lies at the NE foot of a steep hill, that rises an hundred 
yards perpendicular above it, they have half as much more 
rain as I have ; there was 48^- inches last year, as it is set 
down in the first page ; but they had 50^ inches in 1782, 
which is something more. But I was surprised to see, in the 
Supplement to the Gentleman's Magazine, page 1197, that 
Mr. Gough says there was 83^ inches of rain at Kendal last 
year. This is an astonishing quantity ; though it is a hilly 
country, it is almost four times my common year, and above 
double the greatest ; and I should have thought it enough, in 
latitude 54 0 , to have made the whole country a marsh. 


PRESENTS 


1792. 
Nov. 8 


RECEIVED BY THE 


ROYAL SOCIETY, 

From November 1792 to June 1 793. 


WITH THE 


NAMES OF THE DONORS* 


PRESENTS. 

. Memoires de l’Academie Royale des Sciences. 
Aout, 1786, jusqu’a la fin de 1787. Berlin, 
1792. _ _ 4° 

Transactions of the Society for the Encourage- 
ment of Arts, Manufactures, and Commerce, 
Vol. X. London, 1791. 8° 

Memoirs of the Medical Society of London, Vol. 

III. London, 1792. 8° 

Catalogus Bibliothecae Harvardianae Cantabri- 

giae Nov-Anglorum. Bostoniae, 1790. 8° 

Jos. Gaertneri de Fructibus et Seminibus Planta- 
rum, Volumen alterum. Tubingae, 1791. 4 0 

Discours qui ont e'te lus dans 1 ’Assemblee pub- 
lique de l’Academie des Sciences de Berlin, te- 
nue le 26 Janv. 1792. Berlin, 1792. 4 0 

N. J. Jacquin Collectanea ad Botanicam, Che- 
miam, et Historiam Naturalem spectantia, Vol. 

IV. Vindobonae, 1790. 4 0 

Medical Facts and Observations, Vol. III. Lon- 
don, 1792. 8° 

ConnubiaFlorum, Auctore D. Dela Croix ; Notas 
et Observation's adiecit R. Clayton. Bathoniae, 
1791. 8° 

The Sportsman’s Directory, or Tractate on Gun- 
powder, by G. Montagu. London, 1792. 8° 

An Essay upon single Vision with two Eyes, by 
W. C. Wells, M. D. London, 1792, 8° 

2 H 


DONORS. 

The Royal Academy of 
Sciences of Berlin. 

The Society for the En- 
couragement of Arts, 
Manufactures, and 
Commerce. 

The Medical Society of 
London. 

The Corporation of Har- 
vard University, in 
America. 

Sir Joseph Banks, Bart. 
P. R. S. 

Comte de Hertzberg, 
F. R. S. 

Professor de Jacquin, 
F.R.S. 

Samuel Foart Simmons, 
M.D. F.R. S. 

Sir Richard Clayton, 
Bart. 

George Montagu, Esq. 

William Charles Wells, 
M. D. 


MDccxcin. 


C 2 3° 3 


PRESENTS. 

The Rise, Progress, and present State of Medi- 
cine ; a Discourse delivered before the Middle- 
sex Medical Association, by B. Waterhouse. 
Boston, 1792. 8° 

Prodromo di Fisica Vegetable di A. Comparetti. 

Padova, 1791. 8° 

Lettere due del Sig. M. C. al cel. Sig. M. G. 
Padova, 1791. 8° 

Nov. 15. Discours qui a remporte le Prix a l’Academie de 
Chalons en l’Annee 1783. Beauvais, 1789. 4 0 

A Descriptive Account of a Descent made into 
Penpark-hole, in the year 1775. Bristol, 1792. 

8 ° 

22. A Botanical Arrangement of British Plants, by 
W. Withering, Vol. III. Birmingham, 1792. 8° 
Commentarii de Rebus in Scientia Naturali et 
Medicina gestis, Volumen XXXIII. Lipsise, 
1791. 8° 

Museum Leverianum, No. 3 and 4. 4 0 

J. Dickson Fasciculus secundus Plantarum Cryp- 
togamicarum Britanniae. Londini, 1790. 4 0 

Dec. 6. Cases of the Hydrocele, by T. Keate. London, 
1788. 8° 

Principles of Surgery, by J. Pearson, Part I. Lon- 
don, 1788. 8° 

Dissertation sur les Causes qui ont produit i’Es- 
pece de Contradiction qua l’on remarque enrre 
deux Decrets de PAssemblee Nationale. 8° 

13. Transactions of a Society for the Improvement of 
Medical and Chirurgical Knowledge. London, 
1793 - 8 ° 

Collections for an History of Sandwich, by W. 

Boys. Canterbury, 1792. 4 0 

Memoir on the Use of the Thermometer in Na- 
vigation, by J. Williams. Philadelphia, 1792. 

4 ° 

20. Astronomisches Jahrbuch fiir das Jahr 1795, von 
J. E. Bode. Berlin, 1792. 8° 

Projet des Orbites Paraboliques de 72 Cometes, 
dont le Cours a ete calcule jusqu’ici, reduite au 
Plan de l’Orbite de la Terre, par M Bode. 

foi pat. 

A Treatise on the Hydrocele, by J. Earle. Lon- 
don, 1791. 8° 

A short Account of the Life of Mr. Percival Pott. 

8 ° 

A Case of Extra-Uterine Gestation, of the Ventral 
Kind, by W. Turnbull. London, 1791. 4 0 

1 793 * 

Jan. 10. Kongl. Vetenskaps Academiens Nya Handlingar, 
Tom. XII. for 1791, 3d and 4th quarter; 


DONORS. 

Professor Waterhouse, of 
Cambridge, in Ame- 
rica. 

Professor Comparetti, of 
Padua. 


M. Bucquet, of Beau-* 
vais. 

Mr. George Symes Cat- 
cott. 

William Withering, 
M. D. F.R. S. 

Mr. Hurlock, F. R. S. 


Mr. James Parkinson. 
Mr. James Dickson. 

T. Keate, Esq. 

Mr. John Pearson. 

M. Hourcastreme. 


The Society for the Im- 
provement of Medical 
and C hi rurgicai Know- 
ledge. 

William Boys, Esq. 

Mr. Williams, Secretary 
to the American Phi- 
losophical Society. 

Mr. J. E. Bode, F. R. S. 


James Earle, Esq. 

Mr. William Turnbull. 

The Royal Academy of 
Sciences of Stockholm. 


[ 231 3 


DONORS, 


PRESENTS. 

and Tom. XIII. for 1792, 1st and 2d quarter. 
Stockholm. 8° 

Extrait des Observations Astronomiques et Phy- 
siques, faites a l’Observatoire en l’Annee 1791. 

4 ° 

Medical Commentaries for the Year 1792, col- 
lected by A. Duncan. Edinburgh, 1793. 8° 

1 7. An Excursion to the Peak of Teneriffe in 1791, 
by Lieut. Rye. London, 1793. 4 0 

24. Saggio d’Osservazioni concernenti li nuovi pro- 
gress! della Fisica di Corpo Umano, di Stef. 
GalFni. Padova, 1792. 8° 

31. A Plan of a Course of Lectures on the Principles 
of Natural Philosophy, by S. Vince. Cam- 
bridge, 1793. S° 

Practical Observations on Cancerous Complaints, 
by J. Pearson. London, 1793. 8° 

Description d’une nouvelle Presse d’Imprimerie, 
inventee par Guill. Haas, Pere. Basle, 1791. 4 0 
Ftb. 14. Contemplatio Philosophica, a posthumous work 
of Brook Taylor, with a Life of the Author, by 
Sir W. Young. London, 1793. 8° 

An Essay on the Disease produced by the Bite of 
a mad Dog, or other rabid Animal, by J . Mease. 
London, 1793. 8° 

A Sermon preached before the Lords, January 30, 
1793, by Samuel Lord Bishop of St. David’s. 
London, 1793. 4 0 

An Essay on Generation, by J. F. Blumenbach, 
translated from the German. London, 1793 

12 ° 

Museum Leverianum, No. 5. 4 0 

March 7. Elements of Jurisprudence. London, 1783. 4 0 


»4- 

April 11. 


A Systematical View of the Laws of England, by 
R. Wooddeson, III. Vols. London, 1792. 8° 
De Calculo Integralium, Exercitatio P. Ferronii. 

Florentite, 1792. 4 0 

Histoire de la Noblesse Hereditaire des Gaulois, 
par C. J. de Bevy. Tome I. Londres, 1791. 4 0 
Elogio d’ Amerigo Vespucci, delP. Stan. Canovai, 
!79°. _ 4 0 

The literary Life of the late Thomas Pennant, 

Esq. by himself. London, 1793. 4 0 

The Doctrine of Universal Comparison, or Ge- 
neral Proportion, by J. Glenie. London, 1789. 

4° 

Observations on Construction, by J. Glenie. 8° 
Memoire sur la Troisieme Annee du Regne de 
Frederic Guillaume II. Roi de Prusse, lu dans 
l’Assemblee publique de l’Academie des Sci- 
ences de Berlin, le 1 Octobre, 1789, par le 
Comte de Hertzherg. 8° 


M. Cassini, F. R. S. 


Andrew Duncan, M. D. 

Lieutenant Rye. 

Professor Gallini, of Pa- 
dua. 

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F.R.S. 

Mr. John Pearson. 

M. Haas, of Basle. 

Sir WilliamY oung, Bart. 
F. R.S. 

John Coakley Lettsom, 
M.D. F.R. S. 

The Lord Bishop of St. 
David’s, F. R. S. 

A. Crichton, M. D. 


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Richard Wooddeson, 
D. C. L. 


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Pisa. 

Abbe de Bevy. 

Father Gaetano del Ric- 
ca, of Siena. 

Thomas Pennant, Esq. 
F.R. S. 

James Glenie, Esq. 


Comte de Hertzberg, 
F.R.S. 


2 H 2 


C 232 j 




PRESENTS. 

Memoire sur les Revolutions des Etats, lu dans 
l’Asseroblee publique de 1’ Academie des Sciences 
de Berlin ie 6 Octobre, 1791, par le Comte de 
Hertzberg. 8° 

Preis-schriiten von der anwendbarkeit der Kop- 
pelwirthschaft in der Mark Brandenburg, 
nebst bemerk ungen des Grafen von Hertzberg 
iiber eben diesen gegendstand. Berlin, 1793. 8° 
E. F. von Hertzberg ; auszug aus Weidlichs bio- 
graphie der jeztlebenden Rechtsgelehrten. 8° 
Auszug aus Forsters erinnerungen betrelFend den 
Gr. von Hertzberg. 8° 

Lectures on the Elements of Farriery, by C. Vial 
de Sainbel. London, 1793. 4 0 ; with a set of 
Models of Horses Hoofs and Shoes. 

18. Historical View of Plans for the Government of 
British India, 1792. 4 0 

May 9. Substance of the Speech of the Right Honourable 
Henry Dundis, on the British Government and 
Trade in the East Indies, April 23. 1793. 4 0 

A Sketch of two Boats and a Cutter, with sliding 
Keels, agreeable to a Scheme suggested by Cap- 
tain Schank. fol. pat. 

Practical Essays on the Management of Pregnancy 
and Labour, by J. Clarke. London, 1793- 8° 

16. The Military Antiquities of the Romans in North 
Britain, by W. Roy. London, 1793. fol. 

The Theory and Practice of finding the Longitude 
at Sea or Land, by A. Mackay. London, 1793. 

8 ° 


30. The Transactions of the Royal Irish Academy, 
Vol. IV. Dublin. _ 4 0 

Considerations on the Utility of the National 
Debt, by E. King. London, 1793. 8° 

June 6. The antecedental Calculus, by J. Glenie. Lon- 
don* 1793. a 4° 

13. Analyse du Systeme Absorbant ou Lymphatique, 
par R. Desgenettes. Paris, 1792. 12° 

20. Oriental Repertory, Vol. I. published by A. Dal- 
rymple- London, 1793. 4° 

A new System of the Spleen, by N. Robinson. 

London, 1729. 8° 

An Essay on the Materia Medica, by J. Moore. 

London, 1792. 8° 

On Electric Atmospheres, by E. Peart. Gainsbo- 
rough, 1793. 8° 

Theorie des Vents, par M. le Chev. de la Cou- 
draye. Fontenay, 17S6. 8° 


DONORS. 

Comte de Hertzberg, 
F. R.S. 


Mr. Vial de Sainbel. 


The Right Hon. Henry 
Dundas. 

JohnBruce, Esq. F. R. S. 


Captain Schank, of the 
Royal Navy. 

John Clarke, M. D. 

The Society of Anti- 
quaries. 

Mr. Andrew Mackay. 


The Royal Irish Aca- 
demy. 

Edward King, Esq. 

F. R. S. 

James Glenie, Esq. 
F. R. S. 

Rene Desgenettes, M. D. 

Alexander Dalrymple, 
Esq. F. R. S. 
Jonathan Watson, Esq. 
F.R. S. 

Mr. James Moore. 

E. Peart, M. D. 

C hevalier de la Coudraye. 


INDEX 


TO THE. 

PHILOSOPHICAL TRANSACTIONS 


FOR THE YEAR 1793. 


A page 

Abernethy, Mr. John. Account of two instances of uncom- 
mon formation in the viscera of the human body, - 59 

Alverstohe , Hants. Account of two rainbows, seen there at the 

same time - - - - 1 

Atlas East-India ship. Abstract of the journal of, - - 190 

Atmospheres, electrical , their effects upon frogs, and other small 
animals, - - - - 1 1 

B 

Barker, Thomas, Esq. Abstract of a register of the barometer, 
thermometer, and rain, at Lyndon, in Rutland, with the rain in 
Surrey and Hampshire, for the year 1792; and a comparison 
of wet seasons, - 220 

Barometer , register of, at Lyndon, in Rutland, - - 220 

Bay of Biscay, remarks on, - - _ - 187 

Bell, Mr. William. Description of the double horned rhino- 
ceros of Sumatra, - - 3 


INDEX. 


page 


Bell, Mr. Wi lliam. Description of a species of chastodon, 
called, by the Malays, Ecan botina, - 7 

Benares , further particulars respecting the observatory there, - 45 

Account of the method of making ice there, - 56, 129 

Bile , instance of its secretion from arterial blood, - - 61 

Blagden, Sir Charles, Knt. Extract of a letter from, giving 

some account of the tides at Naples, - 168 

Blood vessels , uncommon state of, in the human body, - 60 

c 

Canal , alimentary , uncommon formation of, in the human body - 6 4 

Caterpillars , not affected by electricity, - 32 

Chcetodon, description of a species, called, by the Malays, Ecan 
bonna , - 7 

Ciliary processes, opinions respecting their use, - 170 

Circle , its advantages for astronomical purposes, - 93 

■ of brass, description of one in the observatory at Benares 47 

Clarke, John, M. D. Description of an extraordinary produc- 
tion of human generation, with observations, - - 154 

Clock , description of one of a peculiar construction, - 87 

Coating , metallic , its use in experiments of animal electricity, - 18 

• — of different metals, in what cases necessary, - 20, 24 

Colon , uncommon length of, in the human body, - - 64 

Comet, account of the discovery of one, - - 50 

• of 1793, observations of, - - 55 

Crystalline lens, muscularity of, supposed by Descartes, and Dr. 

Pemberton, - - - - - 170 

discovered by Leeuwenhoek, - 176 

of an ox described, - - - 172 

of fishes, remarks on, - - 177 

Current, observations on one that prevails to the westward of 
Scilly, - - - - 182 

D 

Dial, equinoctial, description of one in the observatory at Benares, 47 
Discoveries, account of some, made by Mr. Galvani, of Bologna, 10 


E 

Ecan bonna, description of a species of chaetodon so called, by 
the Malays, - ~ 

Electric atmospheres, their effects on frogs, and other small animals. 


7 

i 

11 


INDEX. 


page 

Electricity, new discovered law in, - - -20,31 

■ estimate of the quantity necessary to produce certain 

effects in a frog, - - - 15 

■ animal , account of the discovery so called, - 10 

Electrometer , a new kind, called an animal one, - 16 

Equatorial instrument , account of, - - 67 

Evaporation , remarks on its power in generating cold, - 130 

Eye, experiments on, - - * - 179 


F 


Fishes, remarks on their crystalline lens, - - 177 

Fluids, description of an instrument for ascertaining the specific 

gravities of, - - - 164 

Foetus , remarks on the powers and functions of, - - 161 

Frogs, effect of electric atmospheres upon them, - - 11 

experiments with, - 24, 29, 38 


G 


Galvani, Air. Account of some discoveries made by him, - 10 

Generation , human., description of an extraordinary production of, 154 
Gravities, specific, of fluids, description of an instrument for as- 
certaining, - - 164 

Gr egory, -the Rev. Edward. Extracts of two letters from, 
containing an account of the discovery of a comet, with obser- 
vations, - - - - -30 

H 

Hampshire, register of rain in that county, - - 220 

Heart, uncommon transposition of, in the human body, - 60 

Hector East- India ship,, effects of a current upon, - 189 

Hekschel, William, LL. D. Observations on the Planet Ve- 
nus, - - 201 

Human body , uncommon formation in the viscera of, 59 


I 

Ice , account of the method of making it at Benares, 
Immersion of y Tauri, obser vation of, 

Insects, some kinds not affected by electricity, 
experiments on. 


- 56, 129 

- 53 

- 3 2 

- 33 


INDEX. 


page 

Instrument for ascertaining the specific gravities of fluids, de- 
scription of, - - - 164 

Intestines , uncommon formation of, in the human body, - 64 

Journal of the Atlas East-lndia ship, abstract of, - 190 

L 

Lamp micrometer , remarks on, - - 2 1 5 

Levels one of extraordinary sensibility described, - 92 

Leyden phial , remarks on the supposed analogy of, to some phae- 

nomena of animal electricity, - - -19,29 

Light house , remarks on that of Scilly, - 198 

Liver , uncommon state of, in the human body, - 61 

Lizards , experiments on, - - 38 

M 

Maskelyn e, the Rev. Nevil, D. D. Observations of the comet 

of 1793, made by him, and other observers, - 55 

Monster, description of an extraordinary one, - 154 

— remarks on monsters, - - 157 

Mountains said to have been seen in Venus, remarks on, - 202 

Muscles , experiments on muscles, and pieces of muscle, - 28, 30, 35 

not immediately affected by electricity, - - 21, 36 

— voluntary ones not affected by weak currents of electri- 
city, - - - - -34 

Muscularity of the crystalline lens, supposed by Descartes and Dr» 

Pemberton, - - - - - 170 

-discovered by Leeuwenhoek - 176 

Musschenbroek, attempt to solve some optical queries proposed 

by him, - - - - -178 

N 

Naples, some account of the tides there, - - 168 

Nerves, the on y parts immediately affected by electricity, - 21, 36 

— experiments on, - - 23 

o 

Observatory at Benares, further particulars respecting, - 45 

Optical queries , attempt to solve some - 178 

Ox, the crystalline lens of, described, - 172 


INDEX. 


P P a g e 

Parallactic machine , remarks on an instrument so called, - 73 

Placenta , remarks on its vessels, - - 160 

Porous vessels , their use in making ice, - 57 

experiments on the effect of the evaporation pro- 
duced from them, - - - 129 

Presents received by the Royal Society, from November 1792 to 

June 1793, - - - - - 229 

Production, extraordinary, of human generation, - 154 

Projection table, remarks on an instrument so called, - 215 

Q 

Quadrant of stone, in the observatory at Benares, described, - 46 

Quadrupeds, experiments on, - - 23, 25, 27 

Queries , optical , attempt to solve some, - - 1 7 8 

R 

Rain in Rutland, Surrey, and Hampshire, register of, - 220 

comparative tables of, - - 223 

Rainbows, account of two, seen at the same time, 1 

Ramsden, Mr. Jesse, description of an instrument made by him, 75 
Rennell, James, Esq. Observations on a current that often 
prevails to the westward of Scilly ; endangering the safety of 
ships that approach the British Channel, - 182 

Rhinoceros, double horned, of Sumatra, description of 3 

S 

Saturn, remarks on some appearances said to have been seen in 
that planet, - - - 202 

Schmeisser, John Godfrey. Description of an instrument for 
ascertaining the specific gravities of fluids, - - 164 

Scilly, observations on a current that often prevails to the west- 
ward of, - - - - -182 

remarks on the light-house there, - - 198 

Short, Air. Janies, first applied -a telescope to a combination of 
circles, - - - _ -71 

Shuckburgh, Sir George, Bart. An account of the equatorial 

instrument, - - - -67 

Smeaton,Mr . account of an experiment made by him, - 185 

2 I 


MDCCXCIII. 


INDEX. 


page 

Soundings , proposal respecting, between the parallels of Scilly and 

Ushant, - - - 198 

Sturges, the Rev. Dr. An account of two rainbows, seen at the 
same time at Alverstoke, Hants, July 9, 1792, - 1 

Sumatra , description of the double horned rhinoceros of, - 3 

Surrey , Register of rain in that county, - - 220 

T 

Tatties , a kind of mat so called, their use in cooling rooms, - 130 

Tauri y , observation of an immersion of, - - 53 

Thermometer , state of, at Benares, - - - 1 30 

— register of, at Lyndon, in Rutland, - 220 

Tides , at Naples, some account of, - - - 168 

- — - effect of wind on them, ~ - 185 

Tongue , human , experiment upon, - - 42 

Tongues of quadrupeds, experiments with, ~ 43 

Transit circle , description of one, - - 133 

Tumors , remarkable ones on the bones of a fish, - 8 

U 

Uvea , supposed by Dr. |uxin to be muscular, - - 171 

V 

Vascular system , remarks on its powers, - ' 161 

Venus , observations on, - - - 201 

— remarks on the size of diat planet, - - 217 

Viscera of the human body , uncommon formation in, - 59 

Vision , observations on, - - - - 169 

Volta, Mr. Alexander. Account of some discoveries made by 
Mr. Galvani, of Bologna; with experiments and observations 
on them, - - - 10 

w 

Wall , circular , in the observatory at Benares, described, - 48 

Weather of 1 792, remarks on, - - 221,226 

Wet seasons , comparison of, - 223 

Williams, John Lloyd, Esq. Further particulars respecting 
the observatory at Benares, of which an account, with plates, 
is given by Sir Robert Barker, in the LXVIIth Vol. of the 
Philosophical Transactions, - - - 45 


INDEX. 


page 

Williams, John Lloyd, Esq. Account of the method of 
making ice at Benares, - - 56 

additional observations on the me- 
thod of making ice ai rienares, - - 129 

Windy remarks on its effect on water, - 185 

Wollaston, the Rev. Francis, LL. B. A description of a 
transit circle, for determining the place of celestial objects as 
they pass the meridian, - - - 133 

Worms , the class of animals so called not affected by electricity, 32 
experiments on, - - - 32 

Y 

Young, Thomas. Observations on vision, - - 169 

Ts, of a peculiar construction, described, - — 137 


From the Press of 
W. BULMER & Co. 
Cleveland-Row, St. James's. 


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